Search Autocomplete — Simple

Problem statement (interviewer prompt)

Design the autocomplete that powers a search box. As the user types, return the top 5–10 suggestions in <100ms p99. Handle typos, multilingual queries, trending boost, personalization, and an index that updates near-real-time as new queries come in.

flowchart LR
  U([User keystrokes])
  API[Suggest API]
  T[Trie / Cache<br/>top-k per prefix]
  L[(Top-k Store)]
  AGG([Aggregator<br/>query logs -> trends])
  Q[(Query logs)]
  U --> API --> T
  T --> U
  Q --> AGG --> L --> T

    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 API service;
    class T,L,Q datastore;
    class AGG compute;