Do I need PostgreSQL if I'm already using AWS managed services?

Not necessarily.

AWS “managed services” doesn’t mean you need PostgreSQL—it depends on what kind of data and queries your app needs. PostgreSQL is just one database option, and AWS offers managed alternatives.

You might not need PostgreSQL if:

• Your data is simple key-value or document-style
• You need very high scalability with predictable access patterns
• You’re already using AWS-native services like:
  • DynamoDB for NoSQL/key-value
  • S3 for object storage
  • Aurora Serverless / RDS if you want a managed relational DB without self-hosting
  • Redshift for analytics/warehousing
  • ElastiCache for caching

You might want PostgreSQL if:

• You need relational data with joins, constraints, and transactions
• Your app relies on SQL
• You need flexibility for complex queries and reporting
• You want a widely supported database with lots of tooling
• You want Postgres-specific features like:
  • JSONB
  • advanced indexing
  • full-text search
  • extensions

If you mean “managed by AWS,” PostgreSQL can still fit

AWS offers managed PostgreSQL via:

• Amazon RDS for PostgreSQL
• Amazon Aurora PostgreSQL-Compatible Edition

So the real question is not “AWS managed services vs PostgreSQL,” but: Do I need a relational database, and if yes, do I want PostgreSQL as the engine?

Rule of thumb

• Use DynamoDB if your access patterns are simple and scale matters most.
• Use PostgreSQL/Aurora if you need relational integrity, joins, or complex querying.
• Use S3 for files/blobs.
• Use Redshift for analytics.

If you tell me what your app does, I can recommend the best AWS storage/database choice.