SDK Developer Interview Questions

Option B is strongest because it identifies three named principles with precise definitions and articulates the key contrast with internal APIs: SDK consumers cannot be educated at scale, so the design must be self-evident. The pit of success concept is a recognised SDK design pattern that signals experience. Option A states the goal without the principles; every SDK should be easy to use, but that does not explain how to achieve it. Option C makes the important point about audience size and pinned versions, which is the core risk argument for careful SDK design, but it does not describe the design principles themselves. Option D uses CUPID and makes the excellent idiomatic language point with concrete examples — Promises for JavaScript, generators for Python — but it covers all five principles superficially rather than going deep on the most SDK-relevant ones. SDK Developer interview best practice: name the pit of success principle; it is the concept that most directly captures what makes an SDK safe for developers to use without reading the docs.

Option B is strongest because it defines a breaking change precisely across four categories — method removal, signature changes, return type changes, error condition changes — and describes the expand-contract pattern as the implementation strategy. The pattern name is a recognised technique that shows professional experience. Option A defines the concept correctly but at a junior level; "stops working after an upgrade" is imprecise — behaviour changes without compilation errors are also breaking. Option C introduces the API surface test, which is an excellent engineering practice that demonstrates rigour, but it focuses on detection rather than the definition and management strategy. Option D provides the most complete taxonomy — additions, fixes, and breaks — maps each to semantic versioning correctly, and the deprecation registry is a mature operational practice, but it reads as a framework recitation rather than describing how you actually manage the process. SDK Developer interview best practice: define a breaking change more precisely than just "code stops compiling" — behaviour changes, error type changes, and return type changes are equally breaking and often overlooked.

Option B is strongest because it defines three requirements — actionable, typed and hierarchical, context-preserving — and adds the retry-safe flag insight, which is a sophisticated SDK-specific feature that prevents consumers from naively retrying non-idempotent operations. Option A identifies typed errors correctly but gives no design rationale or the actionable message requirement. Option C introduces stable error codes, which are an underrated but important SDK design principle — codes are part of the contract, messages are not — and the documentation point is good, but it covers only one of the three requirements. Option D makes the excellent recoverable versus non-recoverable distinction, which is the most important triage for consumer error handling, and the validation versus runtime separation is a useful design rule, but it does not address error messages, hierarchies, or context preservation. SDK Developer interview best practice: always mention the retry-safe flag or recoverable distinction when discussing SDK errors; it shows you think about how consumers will handle errors in production, not just how they will catch them.

Option B is strongest because it states the governing principle — start minimal — explains the asymmetry of adding versus removing, introduces interface segregation with a consumer-centric framing, and mentions telemetry-driven deprecation decisions. The experimental namespace pattern is a practical technique that non-native English speakers can directly apply. Option A states the goal correctly but with no design principle; "what developers need" is subjective without a process for deciding. Option C articulates the commitment point well — impossible to unexpose — and the promote-on-request practice is good, but it does not describe how to structure the surface or handle experimental features. Option D introduces the primary versus escape-hatch distinction, which is an excellent API design pattern that balances simplicity and power, and the concrete examples — raw HTTP client, custom headers — are realistic, but it does not address the start-minimal principle or how to decide when to promote something to public. SDK Developer interview best practice: say "start minimal and expand" early; it immediately signals you understand the asymmetric cost of public API commitments.

Option B is strongest because it reframes semantic versioning as a communication contract — not just a numbering scheme — lists the three major version release artefacts with specific details — migration guide, LTS branch, codemod — and ends with the consumer-centric goal: no surprises. The 12-month LTS window is a realistic commitment. Option A recites the semver specification correctly but demonstrates no engineering process around it; any developer knows the three version levels. Option C introduces two excellent major release practices — grouping breaking changes and running a beta programme — which show product maturity, but it does not describe the LTS maintenance commitment or the migration guide format. Option D proposes deprecation-driven versioning and the machine-readable deprecation manifest, which are sophisticated practices, and the manifest for IDE tooling is an innovative DX idea, but it focuses on the deprecation process rather than the full major release process. SDK Developer interview best practice: always describe what you deliver alongside a major version release — migration guide, LTS commitment, codemod — not just how you decide when to release one.