▸case-02 For a video rendering API where processing takes up to 10 minutes, a developer wants to hold the HTTP request open until the video finishes rendering and return 200 OK with the rendered MP4 payload. Provide the proper architectural pattern and response headers for handling this long-running operation. | pass→pass | 15,235 | 14,047 | -8% | 1 | 1 | 0% | 3,004 | 2,834 | -6% | 0 | 0 | — |
▸case-01 We are defining a standard error payload format for our public e-commerce HTTP API. A team member suggested returning arbitrary JSON like `{"error": "Invalid item count", "code": 400}`. How should standard error responses be structured across the API to follow established RFC standards? | pass→pass | 15,780 | 14,863 | -6% | 1 | 1 | 0% | 2,623 | 2,833 | +8% | 0 | 0 | — |
▸case-03 We are designing a GraphQL schema for a high-traffic social feed API. The frontend team asks for offset-based pagination using limit and offset arguments because it is simple to implement. Explain why offset pagination is problematic for real-time feeds and specify the standard Relay-compliant GraphQL pagination pattern. | pass→pass | 13,892 | 16,748 | +21% | 1 | 1 | 0% | 2,537 | 3,475 | +37% | 0 | 0 | — |
▸case-04 Our payment processing POST endpoint `/v1/charges` suffers from duplicate billing when clients retry network failures. An engineer proposes using custom query parameters like `/v1/charges?retry_count=1`. What is the standardized HTTP header pattern for ensuring safe retries on non-idempotent HTTP operations? | pass→pass | 7,903 | 13,405 | +70% | 1 | 1 | 0% | 1,494 | 3,009 | +101% | 0 | 0 | — |
▸case-05 Design an OpenAPI 3.0 security scheme snippet for a REST API that authenticates requests using JSON Web Tokens passed in the Authorization header. Avoid using custom header names like X-Auth-Token. | pass→pass | 4,606 | 4,639 | +1% | 1 | 1 | 0% | 840 | 991 | +18% | 0 | 0 | — |
▸case-06 A customer activity log API has millions of entries continuously appended per second. A developer drafted a GET endpoint `/v1/logs?page=5000&limit=50`. Why does this degrade performance and cause skipped or duplicate items, and what parameter design should replace page and limit? | fail→pass | 13,795 | 13,006 | -6% | 1 | 1 | 0% | 2,609 | 2,518 | -3% | 0 | 0 | — |
▸case-07 A client submits a POST request to create a user profile with an email address `user@example.com` that already exists in the database. Another developer suggests returning 400 Bad Request. Which HTTP status codes should be used to distinguish payload schema validation errors from resource state collision errors? | pass→pass | 10,022 | 9,660 | -4% | 1 | 1 | 0% | 1,918 | 1,798 | -6% | 0 | 0 | — |
▸case-08 We need to publish version 2 of an API with breaking schema changes. A developer recommends putting the version in query parameters like `/products?v=2`. Compare API versioning strategies and state the recommended URL path convention versus custom header approaches. | pass→pass | 14,748 | 16,922 | +15% | 1 | 1 | 0% | 2,614 | 3,013 | +15% | 0 | 0 | — |
▸case-09 We are designing an outbound webhook system that sends event notifications to third-party customer endpoints. How should the webhook payload and security signature header be structured to prevent spoofing and payload tampering? | fail→pass | 18,701 | 16,724 | -11% | 1 | 1 | 0% | 3,312 | 3,338 | +1% | 0 | 0 | — |
▸case-10 We are writing an OpenAPI 3.1 specification. In OpenAPI 3.0, nullable fields were defined using `nullable: true`. How should a field that accepts either a string or a null value be typed in OpenAPI 3.1? | pass→pass | 5,853 | 4,576 | -22% | 1 | 1 | 0% | 1,029 | 1,002 | -3% | 0 | 0 | — |
▸case-11 When executing a GraphQL query that fetches a list of 100 posts along with each post's author, the backend issues 1 SQL query for the posts and 100 individual SQL queries for the authors. What architectural pattern resolves this N+1 query problem at the data fetching layer? | pass→pass | 3,483 | 7,770 | +123% | 1 | 1 | 0% | 644 | 1,460 | +127% | 0 | 0 | — |
▸case-12 Design query parameter conventions for a REST API endpoint GET `/v1/orders` that needs to support sorting by creation date descending and filtering by status equal to 'shipped' and total greater than 100. | pass→pass | 10,042 | 12,302 | +23% | 1 | 1 | 0% | 1,915 | 2,439 | +27% | 0 | 0 | — |
▸case-13 Instead of vendor-specific headers like `X-RateLimit-Limit`, what standard IETF RFC draft headers should an API gateway return to inform clients of their current rate limit quota and reset window? | fail→pass | 11,884 | 8,608 | -28% | 1 | 1 | 0% | 2,390 | 1,871 | -22% | 0 | 0 | — |
▸case-14 A junior developer submitted API routes named POST `/create-user`, GET `/getUserById?id=5`, and POST `/updateUserEmail`. Refactor these routes into RESTful resource-oriented endpoints following proper HTTP verb and path conventions. | pass→pass | 9,322 | 8,690 | -7% | 1 | 1 | 0% | 1,856 | 1,897 | +2% | 0 | 0 | — |
▸case-15 In an OpenAPI 3.0 specification for an e-commerce API, duplicate JSON definitions for `Address` appear across user registration, checkout, and shipping endpoints. How should this model be defined once and referenced across endpoints? | pass→pass | 8,481 | 10,514 | +24% | 1 | 1 | 0% | 1,904 | 2,141 | +12% | 0 | 0 | — |
▸case-16 An API client needs to update the status of 500 inventory items at once. Sending 500 individual PATCH requests causes network congestion. Design a RESTful bulk endpoint pattern for updating multiple sub-resources efficiently. | pass→pass | 15,042 | 15,662 | +4% | 1 | 1 | 0% | 2,972 | 3,361 | +13% | 0 | 0 | — |
▸case-21 Write a Kubernetes YAML manifest for a Deployment running 3 replicas of a Node.js API container listening on port 8080 with liveness and readiness HTTP probes targeting `/healthz`. | pass→pass | 6,530 | 7,981 | +22% | 1 | 1 | 0% | 1,196 | 1,576 | +32% | 0 | 0 | — |
▸case-17 In GraphQL schema design, an engineer wants to use an output type containing fields like `created_at` and nested relations directly as an argument type for a mutation `createUser`. Why is this invalid in GraphQL, and what schema structure must be used instead? | pass→pass | 12,123 | 10,852 | -10% | 1 | 1 | 0% | 1,935 | 2,074 | +7% | 0 | 0 | — |
▸case-18 When an administrator deletes an account in an enterprise system, the underlying record is soft-deleted by setting `deleted_at = NOW()` rather than running a SQL DELETE. Compare whether HTTP DELETE or PATCH should be exposed at `/v1/accounts/{id}` and specify the HTTP status code returned upon successful deletion. | pass→pass | 10,124 | 12,007 | +19% | 1 | 1 | 0% | 2,025 | 2,222 | +10% | 0 | 0 | — |
▸case-19 In an OpenAPI 3.0 specification, a payment notification webhook payload can be either a `CreditCardPayment` schema or a `BankTransferPayment` schema depending on the `payment_type` field. How is this request body payload modeled in OpenAPI? | pass→pass | 11,642 | 6,993 | -40% | 1 | 1 | 0% | 2,081 | 1,544 | -26% | 0 | 0 | — |
▸case-20 We have a PostgreSQL table `orders` with 10 million rows. Queries filtering on `user_id` and `created_at` are taking over 3 seconds. Provide a SQL query to create an optimal composite B-tree index on this table. | pass→pass | 6,865 | 5,765 | -16% | 1 | 1 | 0% | 1,323 | 1,157 | -13% | 0 | 0 | — |
▸case-22 Write a React component using TanStack React Query (`useQuery`) to fetch a list of products from `GET /api/v1/products` and render the product names in an un-ordered HTML list. | pass→pass | 5,856 | 5,582 | -5% | 1 | 1 | 0% | 1,196 | 1,355 | +13% | 0 | 0 | — |