Application Programming Interface Design and Communication Questions

Test the candidates ability to design clean application programming interfaces that are intuitive for clients and to clearly explain the design and its trade offs. Coverage includes resource and contract design, request and response formats, error handling and status conventions, versioning and backward compatibility, performance considerations, rate limiting and security basics, and selection of synchronous versus asynchronous communication approaches. At senior levels this expands to event driven patterns, message based systems, gateway patterns, and how interface decisions affect downstream systems and reliability.

HardTechnical

49 practiced

Design authentication token lifecycle and rotation for long-lived API clients such as IoT devices. Include token issuance, refresh, rotation, revocation, offline device handling, heartbeat strategies, secure storage on device, and methods for detecting and responding to token compromise.

HardSystem Design

48 practiced

Architect a gateway that accepts GraphQL queries and composes data by calling multiple backend REST services. Explain how to analyze the GraphQL AST to group field fetches for batching, apply caching at resolver granularity, implement fallbacks or partial responses when backends fail, and how to surface errors according to GraphQL error semantics.

MediumTechnical

41 practiced

For a high-traffic e-commerce checkout, decide whether order creation and payment capture should be synchronous or asynchronous. Evaluate user experience, latency, coupling to payment providers, transactional guarantees, error propagation to clients, eventual consistency, and rollback or compensation strategies.

MediumSystem Design

46 practiced

Design a RESTful product search API for a catalog of 1M products supporting full-text search, filtering (category, price range), sorting, facets (counts), and pagination. Include endpoint signature, query parameters, sample response shape, indexing approach, caching, and trade-offs between using the database vs a search engine like Elasticsearch.

EasyTechnical

37 practiced

Explain contract-first (OpenAPI-first) versus code-first API development. Discuss how each approach impacts documentation quality, SDK generation, design reviews, iteration speed, and coordination with product and client teams in a cross-functional environment.

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