A/B Testing Platform — Simple

Problem statement (interviewer prompt)

Design an A/B testing platform: define experiments with variants, assign users deterministically into variants (sticky bucketing), expose flags to client + server SDKs, collect exposure + conversion events, and compute experiment results with proper statistical significance.

flowchart LR
  U([User])
  ASS[Assignment Service]
  EXP[(Experiment Config)]
  EVT[Events Pipeline]
  ANL[Analysis<br/>p-values, lift]
  U --> ASS --> U
  EXP --> ASS
  U --> EVT --> ANL

    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 U client;
    class ASS,EVT,ANL service;
    class EXP datastore;