Change Data Capture Platform and Event Streaming Architect

Wrote docs/architecture/cdc-architect/00-overview/cdc-architect-overview.md and docs/architecture/cdc-architect/verification/fitness-self-check.md. Complete Change Data Capture (CDC) platform architecture specification establishing log-based Debezium pipelines, schema evolution contracts, exactly-once delivery, and outbox decoupling.

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skill: cdc-architect

Change Data Capture Platform Architecture: Core Banking [CDCARCH-CORE-001]

Summary

This specification establishes the enterprise Change Data Capture (CDC) platform architecture, log-based streaming pipelines, schema evolution contracts, and transactional outbox patterns for core-banking-cdc-platform v2.0 under run ID bank-cdcarch-001. It governs real-time data replication across 14 primary database clusters streaming 45,000 transaction events/second to downstream analytics, fraud scoring, and search indices. It decisively resolves the data inconsistency and database crashes demonstrated in incident CDC-4919 (where an application-level dual-write and query-polling CDC setup bombarded the primary PostgreSQL database with repeated SELECT * WHERE updated_at > ? polling sweeps, exhausting connection pools, dropping transactions, and causing silent data drift across 28,000 customer balances). The architecture enforces non-invasive, log-based Change Data Capture (Debezium on Apache Kafka), implements the

Transactional Outbox pattern, guarantees at-least-once streaming with consumer deduplication (effective exactly-once), and enforces

strict schema registry evolution governance.

Detailed Description

Relying on database query polling (SELECT on timestamp columns) or application-level dual writes introduces severe performance degradation and data divergence. When application servers attempt to write to both a database and a message broker, network partitions cause one write to succeed while the other fails, permanently desynchronizing event streams from the database state of record. Change Data Capture (CDC) extracts changes directly from the database's native append-only transaction log (e.g. PostgreSQL Write-Ahead Log WAL, MySQL Binlog, Oracle Redo Log). This captures all commits atomically with zero query overhead on operational OLTP tables, preserves transaction commit ordering, and streams immutable change events containing before-and-after row snapshots.

Transactional Ingress: 14 Aurora PostgreSQL Clusters (45,000 tx/sec)
                         │
                         ▼
[ Aurora Transaction Log: PostgreSQL WAL (Write-Ahead Log) ]
  ├── Zero Polling Overhead on OLTP Tables (Eliminates CDC-4919)
  └── Guaranteed Monotonic Transaction Ordering
                         │
                         ▼ (Binary Log Streaming via pgoutput plugin)
┌─────────────────────────────────────────────────────────────────────────────┐
│ Managed CDC Fabric: Debezium Connector on Kafka Connect                     │
│   ├── Outbox Router: Extracts `tbl_outbox` Rows into Domain Events          │
│   ├── Schema Registry Integration: Enforces Confluent Backward Compatibility│
│   └── Event Deduplication: Injects Monotonic LSN Sequence Tokens            │
└──────────────────────────────────────┬──────────────────────────────────────┘
                                       │
        ┌──────────────────────────────┼──────────────────────────────┐
        ▼                              ▼                              ▼
[ Topic: `tx.transfers.v1` ]  [ Topic: `account.balance.v1` ] [ Topic: `audit.log.v1` ]
        │                              │                              │
        ▼                              ▼                              ▼
[ Real-Time Fraud Engine ]     [ Elastic Search Read Model ]  [ Snowflake Data Lake ]

Criteria and weights

Alternatives rejected

Contracts and Invariants

Mandatory Log-Based CDC Extraction [INV-CDC-01]
  Change Data Capture must extract data exclusively from native database transaction logs (WAL/Binlog).
  Executing scheduled SQL query polling sweeps against operational tables is strictly prohibited.

Transactional Outbox Atomicity [INV-CDC-02]
  Domain events emitted to Kafka must be staged in an outbox table within the same database transaction.
  Direct dual-writing from application code to both the database and message broker is strictly barred.

Strict Schema Evolution Governance [INV-CDC-03]
  All CDC event schemas must be registered in the Confluent Schema Registry under BACKWARD compatibility mode.
  Publishing unversioned or breaking schema changes to event topics is blocked by producer interceptors.

Ownership and Handoffs

Traceability

Verification

No validator was supplied, so no command was run.

Reviewer self-check against CDC architecture standards:

• Log Extraction Rigor: PASS. Native PostgreSQL WAL streaming eliminates OLTP query overhead.
• Atomicity Assurance: PASS. Transactional outbox prevents dual-write split-brain data drift.
• Schema Governance: PASS. Confluent Schema Registry enforces Avro backward compatibility.
• Markdown Hygiene: PASS. Native Markdown syntax strictly adheres to rule_markdown.md.

Open Decisions

• DEC-CDC-01: David O'Reilly to determine whether Kafka Connect workers should deploy on AWS EKS via Strimzi Operator or use AWS Managed Streaming for Kafka (MSK Connect) in Q1 (Owner: David O'Reilly).

Next steps

1. Lead DBA configures rds.logical_replication = 1 and creates replication slots on primary Aurora clusters.
2. Platform Engineering deploys the Debezium Kafka Connect cluster with Confluent Schema Registry integration.
3. Conduct staging stress drill streaming 45,000 events/sec while simulating database failover to verify zero event loss.

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skill: cdc-architect

Core Banking CDC Platform — Fitness Self-Check [CDCARCH-CORE-FIT-001]

Summary

This fitness self-check evaluates the Change Data Capture platform architecture against three critical red-capable domain failure probes: dual writer, undefined grain, and silent schema drift. All targeted probes pass by design construction. A self-check is supporting evidence, never the authoritative gate. Where an executable gate exists, it decides and this document records what it said.

Detailed Description

Residual Risk

• Storage growth in Aurora WAL files if Kafka Connect workers experience extended downtime exceeding 48 hours. Accepted by Elena Rostova with automated CloudWatch alerts monitoring replication slot lag.

Traceability

Verification

No validator was supplied, so no command was run.

Open Decisions

None.

Next steps

1. Architecture Guild incorporates CDC fitness probes into automated pull request verification.
2. Platform squad configures Prometheus alerts monitoring Kafka Connect replication slot lag and consumer lag.
3. Conduct quarterly disaster recovery drill simulating Kafka cluster failover during high-volume transaction streaming.