How to Choose the Right Database for Your App

Yes, but it is usually expensive and risky. Migrating a production database involves data migration, rewriting queries, testing consistency, and often a period of running both systems in parallel. This is exactly why the initial choice matters: a switch that would take days at launch can take months once you have real data and traffic. Choosing a sensible default like a relational database reduces the odds you will ever need to.

Both are excellent, mature relational databases, and either is a safe choice. PostgreSQL is generally favored for richer features (advanced data types, JSONB, strong extensibility) and strict standards compliance, while MySQL is valued for its simplicity and broad hosting support. For most new applications, PostgreSQL is a strong default, but team familiarity should weigh heavily in the decision.

No. Scale is more often a function of good data modeling, indexing, caching, and infrastructure than of the database category. Relational databases scale to very large workloads with replicas, partitioning, and modern distributed options like Aurora and Spanner. Choose NoSQL for its data model or write characteristics, not because you assume SQL cannot scale.

Enough to avoid an obviously wrong pick, but not so much that it stalls your project. Spend your early effort on a clean data model and a sensible default database rather than optimizing for a scale you do not have yet. Most re-platforming pain comes from a poor data model, not from choosing the wrong product within the right category.

Most mature applications use several databases for different jobs, and that is fine. A common healthy pattern is a relational primary store, Redis for caching, and a search engine for text search. The goal is to use each tool where it is strong while keeping your primary source of truth in one reliable, consistent system.