AI SDK Engineer Interview Questions

A great answer explains that an API is the contract/interface while an SDK is a developer-friendly library that wraps the API with authentication, serialization, error handling, and convenience methods.

Cover generics, discriminated unions, readonly types, and how TypeScript's type system catches API misuse at compile time rather than runtime.

Discuss MAJOR.MINOR.PATCH, backward compatibility guarantees, how developers depend on version ranges, and what constitutes a breaking change.

Describe how OpenAPI specs serve as the single source of truth for API contracts and how code generators use them to produce typed client libraries.

Cover API key headers, OAuth2 bearer tokens, environment variable conventions, credential refresh/rotation, and the principle of least privilege.

A strong answer covers method signatures, options objects vs positional args, generic return types for streaming vs non-streaming, and ergonomic defaults.

Discuss jitter, idempotency, retry-after headers, max retries, distinguishing retryable vs non-retryable errors, and respecting rate limits.

Cover adapter/provider patterns, capability negotiation, graceful degradation when a provider lacks a feature, and configuration flexibility.

Discuss deprecation warnings, gradual removal timelines, migration guides, codemods, and the role of major version bumps.

Cover mocked HTTP clients, snapshot testing of serialized requests, contract tests against a sandbox API, and E2E tests in CI.

Discuss Python asyncio vs sync, TypeScript Promises vs callbacks, the maintenance burden of dual APIs, and patterns like AsyncClient/SyncClient.

Cover a hierarchy of error types (authentication, rate limit, validation, server error), error codes, request IDs, and actionable messages.

Discuss API reference generation, quickstart guides, runnable code samples, migration guides, and interactive sandboxes.

Cover auto-pagination helpers, async iterators, polling with backoff, and webhook-style callbacks for long operations.

Discuss minimal dependency trees, vendoring, peer dependencies, lockfiles, and avoiding transitive dependency bloat.

Discuss mustache/Handlebars templates, AST-based code generation, language-specific linters/formatters in CI, and maintaining custom overrides per language.

Cover SSE parsing, async generators, AbortController integration, buffer management, and graceful cleanup on client disconnect.

Discuss interceptor chains, hook patterns, composability, and reference implementations like Axios interceptors or gRPC interceptors.

Cover connection pooling, thread-local state vs shared clients, HTTP/2 multiplexing, graceful shutdown, and resource cleanup patterns.

Discuss request latency, token usage, error rates, optional OpenTelemetry spans, redaction of sensitive payloads, and sampling strategies.

Cover version negotiation headers, schema evolution strategies, polyfill adapters, and progressive migration patterns.

Discuss conventional commits, semantic-release, matrix CI testing across Python/Node versions, automated changelogs, and canary releases.

Cover generics, fluent interfaces, validation at build time, discriminated unions for content types, and compile-time guarantees.

Discuss error message localization, right-to-left considerations in docs, timezone handling in date fields, and Unicode safety.

Cover unified response types, protocol abstraction layers, fallback strategies, and configuration-driven transport selection.

Discuss dual auth support, deprecation warnings for API keys, migration guide publication, and a phased removal timeline tied to major versions.

Cover improving error specificity, adding troubleshooting links in error messages, pre-flight validation, and measuring issue closure rates post-fix.

Discuss maintenance burden assessment, community demand signals, automated generation feasibility, contribution guidelines, and long-term support commitment.

Cover documentation improvements, singleton client examples, connection pooling defaults, and a lint rule or warning when excessive instantiation is detected.

Discuss runtime-specific fetch implementations, ReadableStream polyfills, testing in miniflare/wrangler, and runtime detection with graceful fallbacks.

Cover hybrid approaches: auto-generation for scaffolding with manual polish, prioritizing high-traffic endpoints, and investing in generation pipeline improvements.

Discuss adapter patterns, new namespace/module design, shared utilities, backward-compatible additions, and co-designing the API with SDK ergonomics in mind.

Cover immediate patch release, credential redaction in logging middleware, automated secret detection in CI, and a security disclosure process.

Discuss configurable HTTP transport, environment variable proxy detection, documentation for proxy setups, and optional dependency injection for the transport layer.

Cover tree-shaking optimization, modular/lazy imports, code splitting, removing polyfills for modern runtimes, and measuring bundle impact in CI.

Discuss JSON Schema generation for tool parameters, type-safe tool definitions, automatic parameter validation, and integration with the chat completions endpoint.

Cover optional dependency patterns, adapter modules, and interface segregation so core SDK works standalone while LangChain integration is a separate install.

Discuss content type discrimination, base64 vs URL encoding, file upload helpers, type guards, and progressive enhancement when a model does not support a modality.

Cover model status polling, warm-up requests, timeout configuration, fallback to alternative models, and user-facing loading state callbacks.

Discuss agent loop implementation, tool dispatch, trace/span creation for each step, configurable max iterations, and structured logging of the full chain.

Cover request coalescing, time-window batching, priority queues, concurrent execution limits, and exposing batch configuration to developers.

Discuss provider abstraction layers, credential management differences, response normalization, and unified error types across providers.

Cover JSON mode parameters, schema validation, retry-on-malformed-output logic, and optional Pydantic/Zod integration for runtime type checking.

Discuss WebRTC or WebSocket transport, audio codec negotiation, bidirectional streaming, buffer management, and graceful degradation.

Cover multipart upload handling, chunking strategies, progress callbacks, embedding generation, and integration with vector database clients.

A strong answer covers stakeholder communication, deprecation timeline, migration tooling, and measurable adoption tracking.

Look for evidence of data-driven persuasion, prototyping alternatives, empathy for the original designer, and collaborative resolution.

Discuss user segmentation, feedback channel analysis, 80/20 prioritization, and balancing simplicity with configurability.

A great answer shows receptivity, rapid iteration, transparent communication with the user, and measurable improvement.

Discuss structured learning routines, monitoring upstream changelogs, community engagement, and how you balance innovation velocity with stability.