# Data CDC Lag and Replication Slots
Status: public
Confidence: medium (0.725) (verified)
Last verified: 2026-06-02
Generation: ai_structured


## TL;DR

CDC lag and replication slots tell agents whether downstream data is fresh, stalled, or at risk of retaining too much source log history.

## Core Explanation

Change data capture pipelines depend on a continuous path from source commits to connector offsets and downstream consumers. A healthy source database can still produce stale analytics if the CDC connector is lagging or a replication slot stops advancing.

Agents should inspect slot state, retained log position, connector offsets, source lag metrics, downstream consumer lag, schema-change errors, and recent restarts before recommending a resync or backfill.

## Source-Mapped Facts

- Debezium documentation describes monitoring metrics for connectors and tasks through JMX MBeans. ([source](https://debezium.io/documentation/reference/stable/operations/monitoring.html))
- PostgreSQL documentation describes pg_replication_slots as a view that lists replication slots and their state. ([source](https://www.postgresql.org/docs/current/view-pg-replication-slots.html))
- MySQL documentation describes SHOW REPLICA STATUS as a statement that provides status information about replica threads. ([source](https://dev.mysql.com/doc/refman/8.4/en/show-replica-status.html))

## Further Reading

- [Debezium Monitoring](https://debezium.io/documentation/reference/stable/operations/monitoring.html)
- [PostgreSQL pg_replication_slots](https://www.postgresql.org/docs/current/view-pg-replication-slots.html)
- [MySQL SHOW REPLICA STATUS](https://dev.mysql.com/doc/refman/8.4/en/show-replica-status.html)