Distributed Tracing — Simple

Problem statement (interviewer prompt)

Design a distributed tracing system (Jaeger / Tempo / Zipkin): collect spans from every microservice, sample intelligently (head + tail), reconstruct end-to-end traces, link traces ↔ metrics ↔ logs, and handle 100k+ trace ingest QPS.

flowchart LR
  S[Service A]
  S2[Service B]
  S3[Service C]
  COL[Collector]
  TR[(Trace store<br/>Jaeger / Tempo)]
  UI[UI]
  S --> S2 --> S3
  S -. span .-> COL
  S2 -. span .-> COL
  S3 -. span .-> COL
  COL --> TR --> UI

    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 S,S2,S3,COL,UI service;
    class TR datastore;