What is the primary benefit of the statelessness constraint in REST?

Statelessness allows requests to be routed to any server instance; no session affinity needed. Each request contains all context, enabling easy horizontal scaling.

Which REST constraint allows responses to be cached by intermediaries like CDNs?

Cacheability constraint defines which responses can be cached and for how long. It enables CDNs and proxies to serve cached responses.

In REST architecture, why is client-server separation important?

Client-server separation allows clients and servers to be developed, deployed, and scaled independently without requiring coordinated changes.

Which URL follows REST naming conventions?

REST naming uses plural nouns (users, not user), lowercase letters, and avoids verbs (getUser). GET already indicates the action.

When designing nested resources, what is the recommended maximum nesting depth?

Maximum 2 levels deep is recommended: /users/42/orders. Beyond that, use query parameters: /orders?userId=42.

What is the key difference between PUT and PATCH?

PUT expects the full resource and replaces it entirely. PATCH accepts partial updates with only changed fields.

Which HTTP method is used to partially update a resource with only changed fields?

PATCH is the correct method for partial updates. POST creates, PUT replaces entire resource, UPDATE is not a standard HTTP method.

What status code should be returned when a POST request successfully creates a new resource?

201 Created indicates successful resource creation. The Location header should point to the new resource.

When should 204 No Content be returned?

204 No Content is used for successful DELETE or other operations where no response body is needed.

What is the difference between 401 and 403 status codes?

401 Unauthorized = client must authenticate. 403 Forbidden = client is authenticated but lacks permission.

Which status code indicates the client sent invalid data that failed validation?

422 Unprocessable Entity is used when syntax is correct but semantic validation fails. 400 is for malformed syntax.

What does 429 Too Many Requests indicate?

429 indicates the client exceeded the rate limit. The server may include Retry-After header.

When would you use 301 Moved Permanently status?

301 indicates the resource has permanently moved. Clients should update bookmarks and caches permanently.

In offset-based pagination with page=2 and limit=10, which records are returned?

With offset-based pagination: page 1 = records 1-10, page 2 = records 11-20, etc. offset = (page - 1) * limit.

What is the main disadvantage of offset-based pagination at scale?

Offset pagination requires database to scan all offset rows first, resulting in O(n) complexity. At large offsets (100k+), this is prohibitive.

Describe the 'data shifting' problem in offset-based pagination.

When new records are added while paginating, offsets become stale. Record at position 11 might become position 12, causing duplicates/skips.

How does cursor-based pagination avoid the data shifting problem?

Cursor stores the last seen record identifier/timestamp. The next query fetches records after that cursor, immune to new inserts.

Which pagination strategy is best for infinite scroll implementations?

Cursor-based is best for infinite scroll: stable pagination, O(1) performance, supports continuous scrolling without jumping.

What is typically encoded in a cursor value?

Cursor typically contains the ID and/or timestamp of the last record, Base64-encoded for obfuscation.

When should offset-based pagination be used over cursor-based?

Offset is simpler for UI with page numbers (page 1, 2, 3) and small datasets. Cursor is better for feeds and scale.

Which versioning approach embeds the version directly in the URL?

URI versioning uses /v1/users, /v2/users. Most common, explicit, and easily testable.

What does the Deprecation header indicate?

Deprecation header signals the API version is deprecated. Often paired with Sunset header specifying removal date.

Which change requires incrementing the API version number?

Renaming a field is breaking; clients expecting 'name' field break when it becomes 'firstName'. Adding optional fields is non-breaking.

Why is header versioning considered more 'RESTful' than URI versioning?

REST philosophy: URI identifies a resource, headers describe metadata. Versioning is metadata, not resource identity.

What is a disadvantage of query parameter versioning?

Query params are semantically intended for filtering/sorting, not versioning. Also breaks caching as each version creates unique cache key.

Which API versioning strategy is used by GitHub and Stripe?

GitHub, Stripe, and most major public APIs use URI versioning for clarity and ease of testing.

What is the recommended deprecation runway before removing an old API version?

Give clients 6-12 months notice with deprecation headers and Sunset date before removing a version.

What naming convention should be used for JSON response fields?

camelCase is the JSON standard; used by most modern APIs. snake_case is Python/Ruby convention, PascalCase looks like class names.

What is the recommended format for timestamps in API responses?

ISO 8601 format (2024-01-15T10:30:00Z) is unambiguous, timezone-aware, and universally understood.

Why use string IDs instead of integers in API responses?

JavaScript numbers exceed precision at 2^53; strings avoid this. Prefixed string IDs (usr_42) also improve readability.

What is the envelope pattern in API response design?

Envelope pattern provides consistent shape: success, data, error (if failed), meta. Aids client parsing and error handling.

What should the response structure look like for an array of resources?

Returning data and pagination together in envelope allows future additions (filters applied, response time, etc.) without breaking clients.

What is the purpose of the meta field in API responses?

Meta field holds requestId (for tracing), timestamp (when response generated), version (API version used), aiding debugging.

In what response header should the URL of a newly created resource be included?

Location header in 201 response points to the newly created resource: Location: /users/42

What should be done when a field is optional but not provided in a request?

Optional fields should be documented. The API can use defaults, omit them, or set to null. Consistency is key.

What is HATEOAS in REST APIs?

HATEOAS (Hypermedia As Engine Of Application State) adds links in responses, enabling clients to discover next actions without hardcoding URLs.

When designing error responses, what should be included?

Error responses should include error code, message, and details (especially field validation errors). Stack traces should never be exposed.

REST API Design Principles — System Design Concept

Q: Which of the following is NOT one of the six core constraints of REST?

The six REST constraints are: statelessness, uniform interface, client-server separation, cacheability, layered system, and code on demand. Asynchronous processing is not a core REST constraint.

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📚REST API Design PrinciplesFree

6 sections

~28 min total

38 quick quizzes

3 SD challenges linked

0 of 6 done·~25 min left

Concepts›REST API Design Principles›What is a REST API?

0 / 6

6 sections~28 min

What is a REST API?

REST is an HTTP-based architectural style enabling client-server communication through stateless, cacheable, uniform interfaces.

ReadQuiz

~5 min

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Resource Naming, HTTP Verbs, Status Codes

Resources are named with nouns in URLs; HTTP verbs define actions; status codes signal request outcomes to clients.

ReadQuizCode

~5 min

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Pagination Strategies: Offset vs Cursor-Based

Offset skips N records then returns M; cursor uses bookmarks for stable, efficient pagination through large datasets.

ReadQuizCode

~5 min

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Versioning: URI vs Header vs Query Param

APIs evolve via URI versioning (/v1/), header versioning, or query parameters to maintain backward compatibility.

ReadQuizCode

~5 min

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Request/Response Shape Design

Consistent request/response envelopes with camelCase fields, typed IDs, ISO dates, and nested objects improve usability.

ReadQuizCode

~5 min

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Practice test

38 questions

~13 min

Section 1 of 6ReadQuick quiz

What is a REST API?

REST is an HTTP-based architectural style enabling client-server communication through stateless, cacheable, uniform interfaces.

~5 min read

3 quick quizzes

A REST API is a way for two computer systems to talk to each other over the internet using standard HTTP. Think of it like ordering food at a restaurant — you (the client) make a request, the waiter (the API) passes it to the kitchen (the server), and you get back a response.

Client ──── HTTP Request ────► Server Client ◄─── HTTP Response ─── Server

REST is built on six core constraints: statelessness, uniform interface, client-server separation, cacheability, layered system, and code on demand (optional).

☑ Quick check 1/3

Which of the following is NOT one of the six core constraints of REST?

AStatelessness

BUniform Interface

CAsynchronous Processing

DCacheability

Answer the quiz to continue

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