System Design (Technical Screen): Database Portion of a Project

Provide a structured description of the database component of a real project you owned. Keep your answer concrete, covering design choices, rationale, and outcomes.

What to Cover

1. Business and performance goals
   • Product context, user journeys, SLOs/SLAs (latency, availability), data retention, compliance/PII, multi-tenancy.
2. Data model and access patterns
   • Core entities, relationships, item sizes, cardinality; top read/write queries and their frequencies; pagination and filters.
3. Datastore selection
   • Chosen datastore(s) (e.g., DynamoDB, Postgres, Elasticsearch), why they fit, and why alternatives were not chosen.
4. Partitioning and indexing strategy
   • Partition and sort keys; sharding; GSIs/LSIs; projected attributes; TTL; hot key mitigation.
5. Consistency settings and semantics
   • Precisely define consistency (e.g., strong vs. eventual, read-after-write, monotonic reads, transactional/ACID scope). Explain implications for read and write paths and user-visible behavior.
6. Trade-off evaluation
   • How you balanced cost, latency, throughput, availability, durability, and operational complexity.
7. Completion and validation
   • What you delivered, how you load/scale tested, correctness checks, shadow/canary, and success metrics.
8. Lessons learned
   • Pitfalls, edge cases, what you would do differently.