PgDog vs Pgpool-II

PgDog is a PostgreSQL connection pooler, load balancer, and database sharder designed to scale databases without application changes. It multiplexes many application connections across fewer PostgreSQL server connections and supports SET, LISTEN/NOTIFY, and advisory locks. Read queries can be distributed across replicas while writes go to the primary, with health checks and failover detection. Sharding keys guide query routing; queries without a key can run across databases in parallel. Cross-shard transactions use PostgreSQL prepared transactions and two-phase commit, with automatic rollback on errors. PgDog can copy data and stream row changes to another database without pausing query traffic. Deployment options include Kubernetes Helm, Docker, AWS ECS Terraform, pre-built binaries, and source. Releases include Linux arm64 and amd64, Apple Silicon Mac, and Debian packages; the macOS binary is unsigned. The project is free and open source under AGPL-3.0, and documentation says internal use does not require sharing source code. Enterprise support includes architecture reviews, a dedicated Slack channel, and an SLA promising a response within 15 minutes.

Pgpool-II is free, self-hosted middleware positioned between PostgreSQL servers and database clients. It relays PostgreSQL protocol messages, reuses matching server connections to reduce overhead, and distributes SELECT queries across replicated databases. High-availability functions include automatic failover, Watchdog, quorum, and split-brain prevention. Additional features include replication, online recovery, connection limiting, and an in-memory query cache. The project is available in binary and source formats, including RPM packages for Red Hat Enterprise Linux and compatible distributions; Debian and Ubuntu users are directed to PostgreSQL community packages. Authentication supports trust, clear-text password, MD5, SCRAM-SHA-256, certificates, PAM, and LDAP, but not GSSAPI. SSL can protect frontend and backend traffic when enabled; it is off by default and requires OpenSSL support. Community assistance is available through mailing lists and GitHub Issues, while SRA OSS K.K. offers commercial support, consulting, and integration. The license permits use, modification, copying, and distribution without a fee.