PostgreSQL
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System Design
PostgreSQL
Relational default for strong consistency, rich queries, transactions, and mature indexing support
Key Points
- PostgreSQL is usually the best starting point for structured application data with clear relationships and transactional requirements.
- It gives you mature indexing, strong consistency, SQL joins, and reliable support for constraints and transactions.
- Many systems can scale surprisingly far with Postgres plus indexes, caching, and read replicas before sharding becomes necessary.
- It is often the source of truth even when secondary systems like Redis or Elasticsearch are added later.
Interview Focus
Default to PostgreSQL unless the access pattern clearly demands something else. Interviewers usually like candidates who start simple and scale only when the numbers force it.