Executive Summary: Comparing JSON index capabilities, concurrency models (MVCC), connection pooling, and replication mechanisms between MySQL and Postgres.

Selecting between MySQL 8 and PostgreSQL 16 is one of the most critical technology decisions when bootstrapping SaaS infrastructure. ### 1. Architectural Comparison - **JSON Processing:** PostgreSQL JSONB indexes binary JSON efficiently using GIN indexes. MySQL 8 has improved JSON functions but handles multi-valued indexing differently. - **Concurrency Control:** PostgreSQL handles heavy concurrent write workloads with minimal lock contention using advanced MVCC. - **Connection Handling:** MySQL uses a lightweight thread-per-connection model. Postgres uses process-per-connection, requiring PgBouncer connection pooling for thousands of clients. ### 2. Summary Recommendation Use MySQL for high-speed read/write web applications with straightforward schemas. Use PostgreSQL for complex analytical queries, geospatial data (PostGIS), or heavy JSONB document querying.