---
title: "Zero-Drift Transactional Outbox via Engine WAL Capture | Distributed Systems Architecture Canon"
description: "Zero-dual-write transactional integration pipeline streaming database mutations from PostgreSQL WAL into Kafka topics using Debezium CDC and Outbox Event Router."
image: "https://tinycto.tv/assets/distributed-systems/distributed_systems_architectures_og.jpg"
canonicalUrl: "https://tinycto.tv/distributed-systems/architectures/debezium-cdc-outbox-pipeline"
locale: "en"
---

# Zero-Drift Transactional Outbox via Engine WAL Capture (`arch-debezium-cdc-outbox-pipeline`)

> **Architectural Pillar**: EVENT_SOURCING_CQRS | **Archetype**: TRANSACTIONAL_OUTBOX_CDC
> **PACELC**: PC/EC | **Consensus Protocol**: None

Zero-dual-write transactional integration pipeline streaming database mutations from PostgreSQL WAL into Kafka topics using Debezium CDC and Outbox Event Router.

### 3 Maturity Target Configurations

#### 1. Initial Target: 4,000 events/sec

- **Guarantees**: At-Least-Once Delivery to Kafka
- **Infrastructure Topology**: Single Debezium server instance tailing PostgreSQL replication slot `pgoutput`.
- **Operational Trade-Off**: If Debezium server stops, PostgreSQL WAL accumulates on disk, risking database storage exhaustion.

#### 2. Scaled Target: 35,000 events/sec

- **Guarantees**: Strictly Ordered Outbox Partitioning by Aggregate ID
- **Infrastructure Topology**: 3-node Kafka Connect cluster with automated rebalance and Prometheus WAL lag alerting.
- **Operational Trade-Off**: Requires monitoring PostgreSQL replication slot lag and WAL retention limits.

#### 3. Ultra-Scale Target: 250,000 events/sec

- **Guarantees**: Parallelized Sharded WAL Streaming with Sub-Second Kafka Availability
- **Infrastructure Topology**: Parallel Debezium connector fleet tailing 16 partitioned database shards simultaneously.
- **Operational Trade-Off**: High complexity coordinating schema evolution across multiple independent logical replication slots.

### Handled Failure Modes

- `DS-FAIL-02: Dual-Write Mutation Drift`
- `DS-FAIL-10: Out-of-Order CDC Ingestion`


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