Tyk) — Simple#

Problem statement (interviewer prompt)

Design a production-grade API gateway service (Kong / Envoy / AWS API Gateway): manage API keys, plans, rate limits, transformations, retries, circuit breakers, and observability for 1000s of downstream services with hot-reloadable config and zero-downtime upgrades.

flowchart LR
  C([Client])
  GW[Gateway]
  PLUG[Plugins<br/>auth, RL, transform]
  S[Upstream services]
  C --> GW --> PLUG --> S

    classDef client fill:#dbeafe,stroke:#1e40af,stroke-width:1px,color:#0f172a;
    classDef edge fill:#cffafe,stroke:#0e7490,stroke-width:1px,color:#0f172a;
    classDef service fill:#fef3c7,stroke:#92400e,stroke-width:1px,color:#0f172a;
    classDef datastore fill:#fee2e2,stroke:#991b1b,stroke-width:1px,color:#0f172a;
    classDef cache fill:#fed7aa,stroke:#9a3412,stroke-width:1px,color:#0f172a;
    classDef queue fill:#ede9fe,stroke:#5b21b6,stroke-width:1px,color:#0f172a;
    classDef compute fill:#d1fae5,stroke:#065f46,stroke-width:1px,color:#0f172a;
    classDef storage fill:#e5e7eb,stroke:#374151,stroke-width:1px,color:#0f172a;
    classDef external fill:#fce7f3,stroke:#9d174d,stroke-width:1px,color:#0f172a;
    classDef obs fill:#f3e8ff,stroke:#6b21a8,stroke-width:1px,color:#0f172a;
    class C client;
    class GW edge;
    class PLUG,S service;

See 00-fundamentals/api-gateway for the conceptual model.