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Increased latency for Large Repos (5k+ source files)

Incident Report for Coveralls

Postmortem

Update: Major Performance Optimization Released for Heavy Repo Builds

Triggered by this latest incident, we've released a major optimization to our code that processes large (aka. “heavy”) repos (>=5K source files).

Tests over the weekend of Fri, Oct 9-Sun, Oct 11 show a near 20x improvement in performance per average heavy repo build at lower, weekend volumes. While we expect the optimization to continue to drastically improve build times for these repos (and reduce incidents of increased latency for them), we won’t know what the aggregate improvement is until we are at full volume this week.

We are monitoring to get a sense of where the performance improvement lands, but are hopeful we’ve crossed a significant milestone in how efficiently these builds are processed given the unique challenges they pose.

Posted Oct 11, 2026 - 12:04 PDT

Resolved

This incident has been resolved.
Posted Sep 30, 2026 - 13:11 PDT

Update

The root cause of issues with large repos has been fully addressed. We are continuing to clear some backlogged background jobs. We will continue to monitor and report updates here.
Posted Sep 30, 2026 - 09:25 PDT

Monitoring

Users in Europe and US east coast with large repos (5k+ repos) experienced slow build completion, starting around 2am PST / 5am EST.

Behavior: PRs opened between 2am-6am PST may have slow or missing Coveralls PR comments or status checks.

We have identified the issue and allocated resources to clear a backlog of background jobs. Jobs should clear and builds should complete in the next ~1hr.
Posted Sep 30, 2026 - 06:19 PDT
This incident affected: Coveralls.io Web and Coveralls.io API.