1. pgx-outbox FOSDEM lightning talk 1 Feb 2025 Nikolay Kuznetsov @nikolayk812 1

2. About me Senior software engineer Zalando Helsinki Pre-owned project C → Java → Kotlin → Go 2

3. Dual write problem 3

4. Transactional outbox pattern 4

5. pgx-outbox library 5

6. implements Message Writer (Postgres) Reader Forwarder Publisher (SNS) 6

7. Outbox message type Message struct { ID int64 // generated by Postgres Broker string `validate:"required"` Topic string `validate:"required"` Metadata map[string]string // optional Payload []byte `validate:"required,json"` } 7

8. Outbox writer type Writer interface { // Tx is empty interface to support both pgx.Tx and *sql.Tx Write(ctx, tx Tx, message Message) (int64, error) // pgx transaction only to invoke SendBatch and Prepare methods WriteBatch(ctx, tx pgx.Tx, messages []Message) ([]int64, error) } 8

9. Writer demo 9

10. WAL Reader support Write ahead log (WAL), aka Change data capture (CDC), aka Postgres logical replication Work in progress (WIP) using jackc/pglogrepl 10

11. Thank you! github.com/nikolayk812/pgx-outbox 11