5 exercises — choose the best-structured answer to common GraphQL Developer interview questions. Focus on precise vocabulary, correct use of technical terms, and demonstrating real experience.
Structure for GraphQL answers
Tip 1: Schema-first: define types, queries, mutations, subscriptions before implementation
Tip 2: N+1 problem: DataLoader batching — batch and cache DB calls per request
Tip 3: Federation: Apollo Federation or GraphQL Mesh for composing multiple subgraph schemas
The interviewer asks: "What is the N+1 problem in GraphQL and how do you solve it?" Which answer best demonstrates GraphQL performance expertise?
Option B is strongest because it defines the N+1 problem with a concrete example, names the correct solution (DataLoader), explains the batching and caching mechanisms, and includes the critical implementation detail about per-request scope. Key structure: 1 + N queries → DataLoader batching within event loop tick → per-request cache → new instance per request. Option A confuses the problem with general GraphQL performance. Option C (depth limiting) is a security measure, not an N+1 fix. Option D (DB cache) reduces DB load but does not batch the N+1 resolver calls.
2 / 5
The interviewer asks: "How would you design a GraphQL schema for a multi-tenant SaaS product?" Which answer best demonstrates schema design maturity?
Option B is strongest because it addresses both schema design (pagination, Input types, implicit versioning) and security (IDOR prevention, field-level auth) with specific vocabulary. Key structure: tenantId from JWT → relay pagination → Input types → deprecation not versioning → field-level @auth. Option A is the exact IDOR vulnerability Option B explicitly prevents. Option C (per-tenant endpoints) is operationally unscalable for many tenants. Option D (persisted queries) is a security layer but does not address schema design.
3 / 5
The interviewer asks: "What is Apollo Federation and when would you use it?" Which answer best demonstrates GraphQL federation knowledge?
Option C is strongest because it gives the precise definition of Federation, explains the key directives, and identifies the exact use case (multi-team, independent deployment, coordination bottleneck). Key structure: subgraphs → supergraph → gateway query planning → @key/@external for entity resolution → use when teams want schema ownership. Option A confuses Apollo Federation (open spec) with Apollo Studio (paid product). Option B confuses Federation with schema stitching or module-splitting within a single service. Option D confuses Federation with API versioning.
4 / 5
The interviewer asks: "How do you protect a GraphQL API from abusive queries?" Which answer best demonstrates GraphQL security depth?
Option B is strongest because it covers the full spectrum of GraphQL-specific abuse vectors with the correct tooling at each layer. Key structure: depth limit → complexity budget → persisted queries → rate limiting → introspection off → field auth. Option A (API key only) protects who can call the API but not what they can ask. Option C (timeouts) only mitigates slow queries, not queries that retrieve massive amounts of data quickly. Option D (response size limit) is a crude backstop — expensive queries still execute on the server before being truncated.
5 / 5
The interviewer asks: "What is the difference between a GraphQL query and a subscription?" Which answer best demonstrates GraphQL protocol knowledge?
Option B is strongest because it explains the protocol difference, the transport mechanism, the implementation requirements, and appropriate use cases. Key structure: query (request-response, closes) → subscription (persistent WebSocket, server-push, asyncIterator, pub/sub fan-out). Option A confuses subscriptions with polling or scheduled jobs. Option C is incorrect — subscriptions do not inherently batch updates; each event triggers a push. Option D confuses subscriptions with HTTP/2 multiplexing or persistent HTTP connections.