Zulip outage on Jan 23, 2025

What happened

Zulip reported a major outage starting Jan 23, 2025, 12:29 UTC, affecting Zulip Cloud, Mobile Push Notification Service. It was marked resolved at Jan 23, 2025, 16:00 UTC.

• The incident lasted 3h 31m from first report to resolution.
• It was the 3rd longest of 3 significant outages Zulip reported in the 12 months up to it.
• Zulip had reported no other partial or major outages in the 90 days before it.

Latest update from Zulip

Starting at 2025-01-23 09:24 UTC, Zulip Cloud began to experience an intermittent outage; users may have seen “Server error” responses when attempting to access Zulip, or slower responses if they succeeded. These intermittent effects were caused by Zulip Cloud running out of memory as it attempted to process and respond to a very small number of requests which were extremely memory-intensive. Parts of the Zulip Cloud service automatically restarted to handle this memory pressure, with varying impacts — at its worst, this caused a complete outage from 09:46 UTC to 09:55 UTC. Starting at 12:04 UTC, Zulip Cloud began to have difficulty responding to the volume of users' requests, and began serving “Server error” responses more consistently, due to being over capacity. This may have been triggered by our attempts to diagnose the memory issues; we are still investigating the contributing causes to this. This outage lasted until 12:57 UTC, when we restored service by temporarily disabli

Read Zulip's official incident report ↗

What our independent monitoring saw

Our independent monitoring of Zulip started after this incident, so this report is based on Zulip's status page.

Zulip's overall reliability

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