PostgreSQL vs MySQL: Which Database Should You Choose?

The short answer to PostgreSQL vs MySQL: for a new custom software project, especially one that needs reporting, complex queries and strict data integrity, PostgreSQL should be the default choice. MySQL is still a sound and cheap choice for projects tied to an existing ecosystem (WordPress, many PHP applications) and for simple, read-heavy workloads. Both are free, mature and able to serve millions of users; the difference is not speed but how strictly they protect your data and how flexibly you can query it.

What are PostgreSQL and MySQL?

Both are relational databases: they store data in tables, are queried with SQL and run transactions on an all-or-nothing basis. MySQL was the web hosting standard for years and comes preinstalled on almost every shared host. PostgreSQL stood out for standards compliance, advanced data types and its extension system, and in recent years has become one of the most popular choices for new projects.

The real differences between PostgreSQL and MySQL

• Data integrity: PostgreSQL enforces constraints (CHECK, foreign keys, uniqueness) strictly. With legacy settings MySQL can silently truncate bad data and save it; strict mode must be on.
• Data types: PostgreSQL natively offers JSONB, arrays, date ranges, UUID and full-text search types. MySQL supports JSON, but indexing and querying it is more limited.
• Complex queries: window functions, CTEs and partial indexes are more mature in PostgreSQL; the difference shows in reporting-heavy dashboards.
• Concurrency: PostgreSQL is built on MVCC, where readers do not wait for writers; this helps systems that write heavily and run reports at the same time.
• Ecosystem: MySQL is the default for off-the-shelf CMS and PHP applications; PostgreSQL is more common in custom Node.js, Python and .NET projects.
• Extensions: PostgreSQL gains new capabilities without a separate system through extensions such as PostGIS (maps/location) and pgvector (AI vector search).

Choosing a database is not a performance decision, it is a data integrity decision. No amount of server speed fixes an invoice total that was saved wrong.

Which one fits which project?

PostgreSQL is the right start for ERP, CRM, accounting integrations, B2B ordering, booking and reporting dashboards, where data consistency means money. Being able to block overlapping booking dates at the database level turns a bug in application code into a harmless one.

-- The database rejects overlapping bookings for the same room
CREATE EXTENSION IF NOT EXISTS btree_gist;

CREATE TABLE booking (
  id       bigserial PRIMARY KEY,
  room_id  int NOT NULL,
  period   daterange NOT NULL,
  EXCLUDE USING gist (room_id WITH =, period WITH &&)
);

MySQL makes sense for sites built on WordPress or an existing PHP stack, for teams with deep MySQL experience and for content systems that mostly do simple reads. This choice is closely tied to the WordPress vs Next.js decision.

When should you consider NoSQL like MongoDB?

Document databases are useful for data whose shape changes constantly and whose records are loosely related (logs, activity feeds, free-form product attributes). For connected business data such as orders, stock and customer accounts, the relational model is still safer. In most projects the flexibility you need is covered by a PostgreSQL JSONB column, with no second database to run.

Questions to ask before choosing

• Is the project tied to an off-the-shelf CMS or PHP ecosystem? If yes, MySQL.
• Is there money, stock or booking data where mistakes cannot be undone? Then PostgreSQL.
• Will you need reporting dashboards, complex filters or map/location queries? PostgreSQL.
• Who will handle backups, version upgrades and monitoring? A managed database service reduces that load.
• Is the data yours at handover and can it be exported? Put it in the contract.

Switching databases later is possible but expensive; the risks we cover in data migration from a legacy system apply here too. Whatever you choose, a regular, tested backup and disaster recovery plan is a must.

Conclusion

In PostgreSQL vs MySQL, the winner is the database that fits your data: PostgreSQL for rule-heavy, reporting-heavy custom software; MySQL for simple sites tied to an existing ecosystem. If you want to work out the right data architecture for your project together, see our custom software service or get a quote.