pgflow is a PostgreSQL/Supabase-native workflow orchestration engine for defining and executing typed DAGs as background jobs. The system is split into six coordinated packages: a PL/pgSQL core (pkgs/core) that implements the complete workflow state machine in the database — flows, steps, runs, step states, tasks, retries with exponential backoff, map/reduce fan-out, conditional step execution, skip-cascade propagation, and realtime event broadcasting — plus a type-safe TypeScript DSL (pkgs/dsl) for declaring flows with compile-time-enforced inputs/outputs, a Deno/edge worker runtime (pkgs/edge-worker) that consumes PGMQ messages and executes step handlers via platform adapters (Supabase vs. plain process), a realtime-subscription client library (pkgs/client), and a CLI (pkgs/cli) for scaffolding new Supabase projects. Execution relies on pgmq for task queues, pg_cron for stalled-task recovery and worker health, pg_net for HTTP worker invocation, supabase_vault for credentials, and Supabase Realtime for atomic state-transition broadcasts.
PGMQ (PostgreSQL Message Queue) is a production-grade message queue implemented as a PostgreSQL extension, with a first-class Rust client library. The system provides SQS-style queue operations (send, read, pop, delete, archive, set visibility timeout) entirely within PostgreSQL, using FOR UPDATE SKIP LOCKED for concurrency. It supports FIFO ordering with message group keys, topic-based routing with wildcard patterns, partitioned queues (via pg_partman), unlogged tables for write throughput, and LISTEN/NOTIFY integration with configurable throttling. The Rust client (pgmq-rs) abstracts queue operations behind a generic Queue trait, with implementations for multiple database drivers: sqlx, Diesel (sync and async), rust-postgres, and tokio-postgres. The extension ships with a comprehensive SQL migration system supporting versioned upgrades, a CLI tool for installation, and extensive test coverage including regression tests and client integration tests. The architecture is layered: the PostgreSQL extension provides the core SQL functions and tables, while the Rust client offers a type-safe, async API. This hybrid approach allows users to interact with queues either directly via SQL or through the client library.