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Question 41
Which HTTP status code indicates that a REST API request was successful and a new resource was created?
A) 200 OK
B) 201 Created
C) 204 No Content
D) 202 Accepted
Answer: B
Explanation:
HTTP status codes communicate the outcome of API requests, with different codes indicating specific results. Understanding these codes is essential for proper API implementation and troubleshooting. The 201 Created status code indicates that a REST API request was successful and a new resource was created on the server. This code is specifically used for POST requests that result in resource creation, distinguishing successful creation from other successful operations. When an API returns 201, it typically includes a Location header pointing to the newly created resource’s URI, allowing clients to immediately access the new resource. The response body often contains a representation of the created resource including any server-generated values like IDs or timestamps. Using 201 appropriately follows REST principles and provides clear semantics to API consumers. Option A (200 OK) indicates general success but doesn’t specifically convey that a new resource was created; it’s appropriate for successful GET requests or updates that don’t create resources. Option C (204 No Content) indicates successful request with no response body, typically used for DELETE operations or updates where the client doesn’t need the updated resource returned. Option D (202 Accepted) indicates the request was accepted for processing but processing isn’t complete, used for asynchronous operations where the actual work happens later. Proper status code usage improves API usability by providing clear, standardized communication about request outcomes. Developers should return 201 specifically when POST or PUT requests create new resources, reserve 200 for successful operations that don’t create resources, and use other 2xx codes appropriately for their specific semantics.
Question 42
What is the primary benefit of using OAuth 2.0 for API authentication?
A) Eliminates need for passwords entirely
B) Enables delegated access without sharing credentials
C) Provides faster authentication than other methods
D) Works only with mobile applications
Answer: B
Explanation:
OAuth 2.0 is an authorization framework widely used for securing API access in modern applications. Understanding OAuth benefits is crucial for implementing secure API integrations. OAuth 2.0 enables delegated access without sharing credentials, allowing users to grant applications limited access to their resources without revealing passwords. This delegation model separates authentication from authorization where users authenticate with the authorization server, applications receive access tokens with specific scopes, and resource servers validate tokens without seeing user credentials. OAuth provides significant security advantages including credential protection where passwords never leave the authorization server, limited scope granting only necessary permissions rather than full account access, token expiration enabling time-limited access, and revocability allowing users to revoke application access without changing passwords. The framework supports multiple grant types including authorization code for web applications, implicit for browser-based apps (deprecated in OAuth 2.1), client credentials for service-to-service, and refresh tokens for obtaining new access tokens without re-authentication. OAuth 2.0 is protocol-agnostic working with web, mobile, and IoT applications. Common implementations include social login allowing users to sign in with Google or Facebook accounts, API access for third-party applications, and microservices authorization. Option A is incorrect as OAuth still requires authentication, typically through passwords or other credentials at the authorization server. Option C is wrong as OAuth isn’t necessarily faster and may involve more round trips than basic authentication. Option D is incorrect as OAuth works across all application types, not just mobile.
Question 43
Which Python library is commonly used for making HTTP requests to REST APIs?
A) numpy
B) pandas
C) requests
D) django
Answer: C
Explanation:
Python provides various libraries for different purposes, and selecting appropriate libraries is important for efficient application development. The requests library is commonly used for making HTTP requests to REST APIs in Python, providing a simple and elegant interface for HTTP operations. The requests library simplifies API interactions by providing intuitive methods like get, post, put, delete, and patch matching HTTP verbs, automatic JSON encoding and decoding, session management for persistent connections, authentication support for various schemes, and exception handling for network errors. Basic usage involves importing the library, calling appropriate methods with URLs and parameters, and processing responses. The library handles complexities like connection pooling, timeout management, and redirect following automatically. Response objects provide convenient access to status codes, headers, and body content through text or json methods. Requests supports advanced features including custom headers for API keys or tokens, query parameters for filtering and pagination, file uploads for multipart form data, SSL certificate verification, and proxy configuration. The library integrates well with other Python tools and frameworks. Alternative libraries include urllib built into Python standard library but with less convenient interface, http.client for low-level HTTP operations, and aiohttp for asynchronous requests. For most REST API interactions, requests is the preferred choice due to its simplicity and comprehensive features. Option A (numpy) is for numerical computing, not HTTP requests. Option B (pandas) handles data analysis and manipulation. Option D (django) is a web framework, not specifically for making HTTP requests, though it includes HTTP client capabilities.
Question 44
What does the term “idempotent” mean in the context of REST APIs?
A) Operations that require authentication
B) Operations that produce the same result regardless of how many times they are executed
C) Operations that are very fast
D) Operations that modify data
Answer: B
Explanation:
Idempotency is a critical concept in REST API design affecting reliability and predictability of operations. Understanding idempotency helps design robust APIs and implement proper error handling. Idempotent operations produce the same result regardless of how many times they are executed, meaning multiple identical requests have the same effect as a single request. This property is crucial for handling network failures and retries safely. In REST, GET, PUT, and DELETE are idempotent by design. GET requests retrieve resources without modification, so multiple identical GETs return the same data. PUT requests completely replace resources, so multiple identical PUTs result in the same final state. DELETE requests remove resources, and deleting an already-deleted resource produces the same result (resource doesn’t exist). POST is not idempotent as multiple identical POSTs typically create multiple resources. Idempotency enables safe retry logic where clients can retry failed requests without worrying about unintended side effects like duplicate resource creation or double-charging. When network failures occur, clients cannot always determine if the server received and processed requests, so safe retry depends on idempotency. Implementing idempotency for non-idempotent operations requires additional mechanisms like idempotency keys where clients provide unique identifiers, servers track processed requests, and duplicate requests are detected and handled appropriately. Payment APIs commonly use idempotency keys to prevent double-charging during retries. Option A incorrectly relates idempotency to authentication. Option C confuses idempotency with performance characteristics. Option D incorrectly suggests idempotency relates to whether operations modify data, when actually it’s about consistent effects regardless of repetition.
Question 45
Which data format is most commonly used for REST API request and response bodies?
A) XML
B) JSON
C) CSV
D) Plain text
Answer: B
Explanation:
Data formats determine how information is structured and transmitted between API clients and servers. Choosing appropriate formats affects API usability and performance. JSON (JavaScript Object Notation) is most commonly used for REST API request and response bodies due to its simplicity, human readability, and broad language support. JSON provides lightweight data representation using key-value pairs, arrays, and nested structures that map naturally to programming language data types. Advantages include compact syntax reducing bandwidth usage, native JavaScript compatibility important for web applications, easy parsing in virtually all programming languages, human readability simplifying debugging, and hierarchical structure supporting complex data relationships. JSON has become the de facto standard for modern REST APIs, with most frameworks providing built-in JSON serialization and deserialization. Content-Type and Accept headers specify JSON as application/json. While XML was previously common and remains used in some enterprise systems, JSON has largely supplanted it for REST APIs due to simpler syntax and smaller payload sizes. XML advantages include built-in schema validation through XSD and namespace support for complex documents, making it suitable for certain enterprise scenarios. However, JSON’s simplicity and efficiency make it preferred for most REST API implementations. Other formats like YAML, Protocol Buffers, or MessagePack serve specialized needs but lack JSON’s universal adoption. Option A (XML) is valid but less common in modern REST APIs. Option C (CSV) is suitable for tabular data exports but not general API communication. Option D (plain text) lacks structure for representing complex data.
Question 46
What is the purpose of API rate limiting?
A) Improve API response speed
B) Protect API infrastructure from overload and ensure fair resource allocation
C) Encrypt API traffic
D) Compress API responses
Answer: B
Explanation:
Rate limiting is a critical API management technique that protects infrastructure and ensures equitable access. Understanding rate limiting is important for both API providers and consumers. API rate limiting protects infrastructure from overload and ensures fair resource allocation by controlling the number of requests clients can make within specified time periods. Rate limiting prevents various problems including resource exhaustion where excessive requests consume server capacity, denial of service attacks whether intentional or accidental, cost control for cloud infrastructure with usage-based pricing, and abuse prevention stopping malicious actors or runaway scripts. Common rate limiting strategies include fixed window counting requests per time period, sliding window providing smoother enforcement, token bucket allowing bursts while controlling average rate, and concurrent request limits restricting simultaneous connections. Rate limits are typically expressed as requests per second, minute, or hour, often varying by authentication tier where anonymous users have lower limits than authenticated users, free tiers have basic limits, and premium tiers receive higher allocations. When limits are exceeded, APIs return 429 Too Many Requests status with Retry-After header indicating when requests can resume. Best practices for handling rate limits include implementing exponential backoff, respecting Retry-After headers, caching responses to minimize requests, and optimizing API usage patterns. API providers should clearly document rate limits, provide headers showing remaining quota, and offer monitoring tools for tracking usage. Option A is incorrect as rate limiting doesn’t improve speed, potentially slowing it by rejecting requests. Option C confuses rate limiting with encryption which addresses different concerns. Option D incorrectly associates rate limiting with compression.
Question 47
Which HTTP method should be used to update a partial resource in a REST API?
A) POST
B) PUT
C) PATCH
D) UPDATE
Answer: C
Explanation:
REST APIs use different HTTP methods for various operations, with specific semantics for each. Understanding method semantics ensures proper API design and usage. PATCH should be used to update partial resources in REST APIs, modifying only specified fields while leaving other fields unchanged. PATCH is specifically designed for partial updates where the request body contains only the fields to modify, the server applies changes to existing resources, and unspecified fields retain their current values. This contrasts with PUT which replaces entire resources. For example, updating only an email address in a user profile would use PATCH with just the email field, while PUT would require sending the complete user object with all fields. PATCH provides efficiency benefits by reducing bandwidth for large resources, simplifying client logic by not requiring full resource retrieval before updates, and preventing accidental data loss from incomplete PUT requests. The request body can use various formats including JSON Patch (RFC 6902) with structured operations, JSON Merge Patch (RFC 7396) for simpler merging, or custom formats specific to the API. PATCH operations should be atomic, either fully succeeding or fully failing. Some APIs use POST for updates when PATCH isn’t supported, though this violates REST conventions. PUT remains appropriate for complete resource replacement where clients provide the entire new representation. Idempotency differs between methods where PUT is idempotent but PATCH may or may not be depending on the patch format. Option A (POST) is typically used for creating resources, not updates. Option B (PUT) replaces entire resources rather than partial updates. Option D (UPDATE) is not a valid HTTP method, though it’s used in some other contexts like SQL.
Question 48
What is the primary purpose of API versioning?
A) Track API usage statistics
B) Allow backward-incompatible changes while maintaining existing client functionality
C) Improve API security
D) Reduce server load
Answer: B
Explanation:
APIs evolve over time requiring changes that may break existing integrations. Versioning strategies manage this evolution while maintaining service to existing clients. API versioning allows backward-incompatible changes while maintaining existing client functionality by providing multiple API versions simultaneously. As APIs mature, changes become necessary including new features, modified response structures, deprecated endpoints, or changed business logic. Some changes are backward-compatible like adding optional fields or new endpoints, while others break existing clients such as removing fields, changing data types, or modifying behavior. Versioning enables API providers to introduce breaking changes in new versions while keeping old versions operational, giving clients time to migrate. Common versioning strategies include URI versioning with version in URL path, query parameter versioning adding version to query string, header versioning using custom or Accept headers, and content negotiation through media type versioning. Each approach has tradeoffs regarding visibility, caching behavior, and implementation complexity. Best practices recommend using semantic versioning (major.minor.patch) where major version changes indicate breaking changes, clearly documenting version differences and migration paths, maintaining old versions for reasonable periods, deprecating versions with advance notice, and minimizing breaking changes through good initial design. Version management requires careful planning for code organization, testing multiple versions, database schema compatibility, and eventual version retirement. Options A, C, and D describe different concerns that aren’t the primary purpose of versioning, though versioning strategies may affect these areas indirectly.
Question 49
Which status code indicates that an API request requires authentication?
A) 400 Bad Request
B) 401 Unauthorized
C) 403 Forbidden
D) 404 Not Found
Answer: B
Explanation:
HTTP status codes communicate request outcomes, with specific codes for authentication and authorization failures. Understanding these distinctions is important for security and error handling. The 401 Unauthorized status code indicates that an API request requires authentication, meaning the client must authenticate itself to receive the requested response. Despite its name, 401 actually means “unauthenticated” rather than unauthorized. This status is returned when no credentials were provided, credentials are invalid or expired, or token authentication failed. The response typically includes a WWW-Authenticate header indicating the authentication scheme required such as Bearer for token-based auth or Basic for username/password. Clients receiving 401 should prompt for credentials or refresh authentication tokens. The 403 Forbidden status differs from 401 by indicating the client is authenticated but lacks permission for the requested resource, meaning the server understands who the client is but refuses the request due to insufficient privileges. The distinction is important: 401 means “who are you?” while 403 means “I know who you are, but you can’t do that.” Some APIs blur this distinction for security reasons, using 404 to hide resource existence from unauthorized users, or returning 401 for both authentication and authorization failures to avoid information disclosure. Best practices recommend using 401 for authentication failures, 403 for authorization failures, including helpful error messages in response bodies, and implementing proper authentication flows. Option A (400) indicates malformed requests. Option C (403) indicates authorization rather than authentication failures. Option D (404) indicates resources don’t exist, not authentication issues.
Question 50
What is the purpose of CORS (Cross-Origin Resource Sharing) in web APIs?
A) Compress data transmission
B) Allow controlled access to resources from different origins/domains
C) Encrypt API communications
D) Load balance API requests
Answer: B
Explanation:
CORS is a security mechanism implemented by web browsers to control cross-origin HTTP requests. Understanding CORS is essential for building web applications that consume APIs from different domains. CORS allows controlled access to resources from different origins/domains by enabling servers to specify which origins can access their resources through HTTP headers. Browsers enforce the same-origin policy preventing JavaScript from making requests to different domains, protocols, or ports than the page origin. This security feature prevents malicious websites from accessing user data on other sites. However, legitimate cross-origin requests are common in modern web applications where frontend and backend are on different domains, microservices architecture involves multiple services, or third-party APIs are consumed. CORS provides controlled relaxation of same-origin policy through server-specified headers including Access-Control-Allow-Origin specifying allowed origins, Access-Control-Allow-Methods listing permitted HTTP methods, Access-Control-Allow-Headers indicating allowed request headers, and Access-Control-Allow-Credentials enabling credential inclusion. For simple requests, browsers send requests directly and check response headers. For complex requests, browsers send preflight OPTIONS requests to verify permissions before actual requests. CORS configuration requires careful security consideration where wildcard origins (*) allow any domain but prevent credential inclusion, specific origin lists provide tighter control, and overly permissive settings create security vulnerabilities. Common issues include missing CORS headers, incorrect origin specifications, and preflight request failures. Proper CORS implementation balances functionality with security. Option A describes compression, not CORS. Option C describes encryption like TLS/SSL. Option D describes load balancing infrastructure.
Question 51
Which Python data structure is most similar to JSON objects?
A) List
B) Dictionary
C) Tuple
D) Set
Answer: B
Explanation:
Understanding the relationship between programming language data structures and JSON formats is crucial for API development and data manipulation. Python dictionaries are most similar to JSON objects, both representing key-value pair collections with similar syntax and semantics. JSON objects use curly braces with quoted keys and values, while Python dictionaries use similar syntax with optional key quoting. Both support nested structures, allowing dictionaries/objects within dictionaries/objects. Python’s json module provides seamless conversion between dictionaries and JSON objects through json.dumps() for serialization and json.loads() for deserialization. The natural mapping makes Python ideal for REST API development. JSON arrays map to Python lists, JSON strings to Python strings, JSON numbers to Python int or float, JSON booleans to Python True/False, and JSON null to Python None. When working with APIs, developers frequently convert between these formats where incoming JSON is parsed to dictionaries for manipulation, data is organized in dictionaries, and dictionaries are serialized to JSON for responses. Understanding this correspondence simplifies API development and troubleshooting. Nested dictionaries handle complex JSON structures like embedded objects or arrays of objects. Python’s flexible dictionary manipulation combined with JSON compatibility makes it powerful for API work. Option A (list) maps to JSON arrays, not objects. Option C (tuple) is immutable and doesn’t map directly to JSON structures. Option D (set) has no direct JSON equivalent and isn’t ordered.
Question 52
What does REST stand for in the context of web APIs?
A) Remote Execution and State Transfer
B) Representational State Transfer
C) Resource Encoding and Secure Transmission
D) Rapid Efficient Service Technology
Answer: B
Explanation:
REST is an architectural style that has become the dominant approach for designing web APIs. Understanding REST principles is fundamental for API development and integration. REST stands for Representational State Transfer, describing an architectural style for distributed hypermedia systems defined by Roy Fielding in his doctoral dissertation. REST defines constraints for building scalable web services including client-server separation where client and server concerns are separated, statelessness where each request contains all necessary information without server-side session state, cacheability where responses must define themselves as cacheable or not, layered system allowing intermediaries like proxies or gateways, and uniform interface through standardized resource identification and manipulation. RESTful APIs use HTTP methods semantically with GET for retrieval, POST for creation, PUT for replacement, PATCH for updates, and DELETE for removal. Resources are identified by URIs and represented in formats like JSON or XML. REST’s stateless nature improves scalability since servers don’t maintain session state, simplifies implementation, and enables better load distribution. However, some application requirements like long-running transactions may conflict with statelessness. REST has largely replaced SOAP for web APIs due to simplicity, performance, and alignment with web architecture. While REST is described as an architectural style rather than a protocol, common practices have emerged forming conventions for RESTful API design. Understanding REST principles helps create intuitive, scalable APIs that follow web standards. The other options are fabricated acronyms that don’t represent actual REST meaning.
Question 53
Which authentication method involves including credentials in the Authorization header?
A) Cookie-based authentication
B) Basic authentication
C) Form-based authentication
D) Certificate authentication
Answer: B
Explanation:
Various authentication methods exist for APIs, each with different security characteristics and use cases. Understanding authentication mechanisms is crucial for secure API implementation. Basic authentication involves including credentials in the Authorization header by encoding username and password in Base64 and sending with each request. The header format is “Authorization: Basic ” followed by the Base64-encoded “username:password” string. Basic auth is simple to implement and supported by all HTTP clients and servers. However, it has significant security limitations including credentials sent with every request, Base64 encoding providing no encryption (easily decoded), and vulnerability to interception without TLS/SSL. Therefore, basic auth should only be used over HTTPS connections. Despite limitations, basic auth remains useful for internal APIs, development/testing environments, and situations requiring simple authentication without complex infrastructure. Many APIs use basic auth with API keys instead of username/password, treating the API key as a password. More secure alternatives include OAuth 2.0 with time-limited tokens, API keys in headers (similar security profile to basic auth), JWT tokens with cryptographic signing, and certificate-based mutual TLS. Basic auth is appropriate when simplicity is prioritized and TLS is mandatory, but shouldn’t be used for high-security scenarios or without encryption. Option A (cookies) stores session identifiers in browser cookies. Option C (form-based) uses HTML forms for credential submission. Option D (certificates) uses X.509 certificates for mutual TLS authentication, not Authorization headers.
Question 54
What is the primary advantage of using asynchronous API calls?
A) Simpler code structure
B) Non-blocking execution allowing applications to continue processing while waiting for responses
C) Automatic error handling
D) Reduced network bandwidth usage
Answer: B
Explanation:
Synchronous and asynchronous programming models have different characteristics affecting application performance and responsiveness. Understanding these differences is important for building efficient applications. Asynchronous API calls provide non-blocking execution allowing applications to continue processing while waiting for responses, improving efficiency and responsiveness especially when making multiple API calls or handling I/O operations. Synchronous calls block program execution until responses are received, causing idle time where applications wait for network communication. For single requests, blocking may be acceptable, but when making multiple API calls, synchronous execution becomes inefficient as each request must complete before the next begins. Asynchronous execution initiates multiple requests concurrently, continuing program execution without waiting, and handling responses through callbacks, promises, or async/await syntax. Benefits include improved application responsiveness keeping UIs responsive during network operations, better resource utilization enabling concurrent operations, and reduced total execution time when making multiple independent requests. Asynchronous patterns include callbacks executing functions when operations complete, promises representing eventual completion or failure, and async/await providing synchronous-looking asynchronous code. Modern programming languages and frameworks provide extensive async support. Challenges include increased code complexity, error handling across async boundaries, and debugging non-linear execution flows. However, for I/O-intensive applications like those making many API calls, async provides significant performance benefits. Option A is incorrect as async code is typically more complex. Option C is wrong as error handling still requires explicit implementation. Option D is incorrect as async execution doesn’t reduce bandwidth, just improves efficiency of using it.
Question 55
Which HTTP header is used to specify the format of the request body?
A) Accept
B) Content-Type
C) Authorization
D) User-Agent
Answer: B
Explanation:
HTTP headers provide metadata about requests and responses, with specific headers serving particular purposes. Understanding header usage is essential for proper API communication. The Content-Type header specifies the format of the request body, telling the server how to interpret the payload data. Common Content-Type values include application/json for JSON data, application/xml for XML data, application/x-www-form-urlencoded for HTML form data, multipart/form-data for file uploads, and text/plain for unstructured text. The Content-Type header is crucial for APIs to correctly parse request bodies, with incorrect or missing headers causing parsing failures and 400 Bad Request errors. The header includes media type (MIME type) and optional parameters like charset for character encoding. The Accept header differs from Content-Type by specifying what formats the client can receive in responses rather than what format is being sent. APIs use Accept for content negotiation, returning different representations based on client preferences. For example, a client might send “Accept: application/json” to request JSON responses. Both headers are important for API communication where requests include Content-Type for body format and Accept for desired response format. RESTful APIs typically use JSON as default, though some support multiple formats selected through content negotiation. Proper header usage ensures interoperability and prevents parsing errors. Option A (Accept) specifies desired response format, not request body format. Option C (Authorization) contains authentication credentials. Option D (User-Agent) identifies the client application.
Question 56
What is API throttling?
A) Increasing API response speed
B) Temporarily slowing or rejecting requests to prevent system overload
C) Compressing API responses
D) Encrypting API communications
Answer: B
Explanation:
API throttling is a traffic management technique that protects backend systems and ensures service quality. Understanding throttling helps both API providers and consumers manage resources effectively. API throttling temporarily slows or rejects requests to prevent system overload by controlling the rate at which clients can make requests. Throttling differs slightly from rate limiting though terms are often used interchangeably. Rate limiting typically enforces hard limits rejecting requests beyond quotas, while throttling may slow responses or queue requests rather than immediately rejecting them. Throttling protects against various issues including resource exhaustion preventing server crashes, cost control for cloud services with usage-based pricing, quality of service ensuring fair resource distribution among users, and abuse prevention stopping malicious or buggy clients. Throttling strategies include request queuing where excess requests wait for processing, response delays artificially slowing responses during high load, request rejection returning 429 status for excess requests, and priority-based serving where premium users receive preferential treatment. Implementing throttling requires tracking request counts per client, time windows for rate calculations, and distributed coordination for multi-server deployments. Clients should implement proper throttling handling including exponential backoff for retries, respecting Retry-After headers, implementing local rate limiting to prevent exceeding quotas, and caching responses to minimize requests. Good API design includes clear throttling documentation, monitoring tools for tracking usage, and appropriate limit tiers. Option A is opposite of throttling which constrains rather than increases speed. Options C and D describe compression and encryption which are separate concerns from traffic management.
Question 57
Which design pattern is commonly used to make code more testable when working with external APIs?
A) Singleton pattern
B) Factory pattern
C) Dependency injection
D) Observer pattern
Answer: C
Explanation:
Testable code design is crucial for maintaining reliable applications, especially when integrating external dependencies like APIs. Design patterns facilitate testing by managing dependencies. Dependency injection is commonly used to make code more testable when working with external APIs by allowing test implementations to replace real API clients. Dependency injection provides dependencies to objects from external sources rather than objects creating dependencies internally. For API integration, this means API client objects are passed to classes that need them rather than classes instantiating clients directly. This enables substituting mock or stub API clients during testing, avoiding actual network calls in tests. Benefits include test isolation removing dependencies on external services, faster test execution without network latency, predictable tests unaffected by API availability or rate limits, and ability to test error conditions by simulating API failures. Implementation approaches include constructor injection passing dependencies through class constructors, setter injection providing dependencies through methods, and interface injection where dependencies implement interfaces enabling substitution. Testing with dependency injection uses mock objects simulating API responses, stub implementations returning predefined data, and test doubles replacing real clients. This pattern is fundamental to test-driven development and continuous integration. While applicable beyond APIs, dependency injection is particularly valuable for external service integration where real services are slow, unreliable, or costly to call during testing. Option A (singleton) often hinders testing by creating global state. Option B (factory) helps create objects but doesn’t address dependency management. Option D (observer) manages event notification but isn’t primarily about testing.
Question 58
What is the purpose of API pagination?
A) Improve API security
B) Break large result sets into smaller pages to improve performance and usability
C) Version API endpoints
D) Authenticate API requests
Answer: B
Explanation:
APIs often return collections of resources that may contain hundreds or thousands of items. Pagination techniques manage large result sets effectively. API pagination breaks large result sets into smaller pages to improve performance and usability by limiting the amount of data transferred in single responses. Without pagination, retrieving all records in large collections causes performance problems including excessive memory usage on both server and client, slow response times transferring large payloads, network timeouts for extremely large responses, and poor user experience waiting for unnecessary data. Pagination enables incremental data loading, showing initial results quickly, reducing resource consumption, and allowing users to navigate through data efficiently. Common pagination approaches include offset-based pagination using parameters like limit and offset, cursor-based pagination using opaque tokens pointing to positions in result sets, and page-number pagination using page and pageSize parameters. Each approach has tradeoffs regarding consistency, performance, and implementation complexity. Offset-based pagination is simple but can miss or duplicate records if data changes between requests. Cursor-based pagination handles concurrent modifications better but is more complex. Pagination metadata in responses typically includes total count of records, current page information, links to next/previous pages, and indication of more results. REST APIs often use Link headers following RFC 5988 for pagination links. Best practices recommend reasonable default page sizes, maximum page size limits, consistent pagination across endpoints, and clear documentation of pagination parameters. Proper pagination is essential for scalable APIs. Options A, C, and D describe different API concerns unrelated to managing large result sets.
Question 59
Which HTTP method is considered safe, meaning it should not modify server state?
A) POST
B) PUT
C) GET
D) DELETE
Answer: C
Explanation:
HTTP methods have defined semantics including whether they modify server state. Understanding safe and idempotent methods is important for correct API design and caching behavior. GET is considered a safe HTTP method meaning it should not modify server state, only retrieving resources without causing side effects. Safe methods are read-only operations that don’t alter resources, making them suitable for caching, prefetching, and repeated execution without concern. GET requests should be idempotent and safe, producing the same result when repeated and not changing server data. This doesn’t mean GET cannot have any server-side effects like logging or analytics, but shouldn’t change resource state visible to clients. Safe methods include GET for retrieving resources, HEAD for retrieving headers only, and OPTIONS for discovering supported methods. Unsafe methods that modify state include POST for creating resources, PUT for replacing resources, PATCH for updating resources, and DELETE for removing resources. The safe/unsafe distinction affects caching where safe methods can be cached aggressively, browser behavior enabling prefetching of safe requests, and developer expectations around method effects. API design should respect these semantics, using GET only for retrieval and appropriate unsafe methods for modifications. Some APIs incorrectly use GET for operations with side effects, violating REST principles and causing unexpected behavior like unintended actions from browser prefetching or crawler indexing. POST is sometimes overused for operations that should be other methods due to firewall or infrastructure limitations, but proper REST design uses methods according to their semantics. Option A (POST), B (PUT), and D (DELETE) are all unsafe methods that modify server state.
Question 60
What is the purpose of an API gateway?
A) Store API documentation
B) Provide a single entry point for multiple backend services with cross-cutting concerns like authentication and rate limiting
C) Generate API client libraries
D) Host API servers
Answer: B
Explanation:
Modern architectures often involve multiple backend services requiring coordination and common functionality. API gateways address these needs through centralized management. API gateways provide a single entry point for multiple backend services implementing cross-cutting concerns like authentication, rate limiting, and request routing. Gateways sit between clients and backend services, intercepting requests and applying various policies. Key functions include request routing directing requests to appropriate backend services based on URLs or headers, authentication and authorization validating credentials and permissions centrally, rate limiting and throttling enforcing request quotas, request/response transformation modifying data formats or structures, caching reducing backend load through response caching, logging and monitoring tracking API usage and performance, and SSL termination handling encryption at the gateway. Benefits include simplified client interaction with single endpoint instead of multiple services, consistent policy enforcement across all services, reduced backend complexity moving common logic to gateway, improved security through centralized access control, and better operational visibility. API gateways are particularly valuable in microservices architectures where applications consist of numerous small services, service-oriented architectures requiring service coordination, and mobile or IoT backends needing optimized APIs. Popular API gateway products include Kong, Amazon API Gateway, Azure API Management, and Apigee. Considerations include gateway becoming potential single point of failure, added network hop introducing latency, and gateway configuration complexity. Proper gateway design includes high availability deployment, performance optimization, and clear service routing rules. Options A, C, and D describe different tools or concepts not related to gateway functionality.
