Design a Real-Time Suggestions Service
Company: SoFi
Role: Software Engineer
Category: System Design
Difficulty: hard
Interview Round: Onsite
Design a system that provides real-time typeahead/autocomplete suggestions as users type. Cover API design and request/response schemas, data modeling and indexing (e.g., prefix trees or inverted indexes), ranking signals and personalization, latency targets (e.g., <100 ms P
95), caching layers, scalability, freshness and backfill pipelines, A/B experimentation hooks, and failure handling.
Quick Answer: This question evaluates a candidate's ability to design low-latency, globally scalable real-time typeahead/autocomplete systems, assessing competencies in distributed systems, indexing and search data structures, ranking and personalization, caching, streaming and batch data pipelines, telemetry, and fault-tolerant architecture.