DBLE vs PgCat

DBLE is free, open-source middleware for scaling MySQL through sharding. It uses the MySQL protocol and can replace MySQL in many cases without application code changes. Teams can configure hash, modulo, time-based, range-based, or custom sharding, along with global and ER tables. DBLE lists query routing, connection pooling, load balancing, automatic failover, read/write separation, master-slave expansion, and ZooKeeper cluster deployment. SQL support includes SQL 92 and MySQL dialect features such as joins, unions, grouping, ordering, and distinct queries; some features remain on its roadmap. Query optimization addresses global-table joins, sharded tables, ER relations, and subqueries. Distributed transactions use two-phase commit in normal or XA modes, with XA depending on MySQL 5.7 XA transactions, backend availability, and disk reliability. Security controls include password encryption, IP allowlists, and SQL denylists. Explain plans, MySQL-compatible slow logs, and slow-query reports support operations. DBLE is self-hosted on Linux and GPL-2.0 licensed. The open-source plan costs nothing.

PgCat is a free, open-source PostgreSQL pooler and proxy for self-hosted Linux deployments. Its stable features include transaction and session pooling. Read queries can be balanced across replicas and the primary, while health checks detect broken replicas and redirect queries to remaining servers. PgCat uses Tokio’s asynchronous runtime and a multithreaded design for multicore machines. Operators can view pooler statistics through the pgcat and pgbouncer admin databases or a Prometheus HTTP endpoint. Client and PostgreSQL server connections can use SSL/TLS, with MD5 and SCRAM-SHA-256 authentication supported. MD5 passthrough can use auth_query so cleartext passwords need not be stored in the configuration file. Docker deployment is documented, and a container image is published. Sharding syntax, comment parsing, automatic sharding, and mirroring are experimental. Transaction mode is enabled by default and does not support prepared statements, SET, or advisory locks. The project describes PgCat as stable and says it serves high query volumes in production. It is licensed under MIT.