Outage in PostHog

EU ingestion lag

Resolved Minor
September 04, 2025 - Started 4 days ago - Lasted about 2 hours
Official incident page

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Outage Details

We are having some issues with our ClickHouse cluster not being able to merge parts as expected and it's leading to increased ingestion lag. We are looking into what the root cause could be.
Components affected
PostHog Event and Data Ingestion
Latest Updates ( sorted recent to last )
RESOLVED 4 days ago - at 09/04/2025 06:27PM

We spotted one of our tables receiving way too many inserts and causing issues with replication inside the cluster.

We resolved that and lag is now back to normal.

INVESTIGATING 4 days ago - at 09/04/2025 04:21PM

We are having some issues with our ClickHouse cluster not being able to merge parts as expected and it's leading to increased ingestion lag.

We are looking into what the root cause could be.

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