Outbox Pattern - Quick Reference

// In your service/usecase
func (s *UserService) Create(ctx context.Context, user User) error {
    return s.db.Transaction(func(tx *gorm.DB) error {
        // 1. Save user
        if err := tx.Create(&user).Error; err != nil {
            return err
        }

        // 2. Create event
        payload, _ := json.Marshal(user)
        event := outbox.NewOutboxEvent(user.ID, "UserCreated", payload)

        // 3. Save to outbox (using same transaction)
        return outboxRepo.Save(ctx, event)
    })
}

-- Check pending events
SELECT * FROM outbox_events WHERE published = false;

-- Check failed events (dead letters)
SELECT * FROM outbox_events WHERE published = false AND attempts >= 3;

-- Check recently published events
SELECT * FROM outbox_events WHERE published = true ORDER BY published_at DESC LIMIT 10;

# Test with NATS down
docker stop go_nats
curl -X POST .../register  # Still works! (stored in DB)
docker start go_nats       # Relay worker picks up and publishes