Learn/SEV0
SEVERITY

Severity 0 (Critical)

Critical emergency. The system is completely unusable for a significant portion of users, or data integrity is at risk.

SEV0

Critical emergency. The system is completely unusable for a significant portion of users, or data integrity is at risk.

## "Everything is on Fire" **SEV0 (Severity 0)** is the highest level of emergency. It means the core product is completely broken, detailed user data is being deleted, or a security breach is active. ### Criteria * **Availability**: Critical user flows (Login, Checkout) are failing for >10% of users. * **Data**: Data corruption or loss is occurring. * **Security**: Active intruder or public leak of PII. ### The Response Mode During a SEV0, **process is suspended**. You do not wait for code review. You do not wait for CI. You "break glass" to mitigate impact as fast as possible.

ExThe Black Friday Crash

"An eCommerce site went down completely at 9am on Black Friday due to traffic load."

Impact
Lost $100k revenue per minute.
Resolution
Team provisioned 500 extra servers in 10 minutes, bypassing all cost controls. Revenue recovered.

Why SEV0 Matters

Every second of SEV0 equals lost revenue and trust.

Requires immediate "all hands on deck" response.

Bypasses all standard process changes (e.g., "break glass" to deploy).

Common Pitfalls

Analysis Paralysis
Debating "is this really SEV0" while the system burns. Declare first, downgrade later.
Solo Heroics
Trying to fix a SEV0 alone. You MUST page the team.
Silent Fixing
Fixing the issue without telling anyone, so no one knows *why* it recovered.

How to Use SEV0

🚨
Automated Paging: Ensure PagerDuty/Opsgenie wakes people up.
📢
Status Page: Update status within 5 minutes. Silence breeds panic.
👥
War Room: Open a voice bridge/Zoom immediately.

Related Terms

Severity 1Incident CommanderStatus Page

Frequently Asked Questions

Who declares a SEV0?
Anyone. If you think it is a SEV0, declare it. Better to false alarm than to delay.
Do I wake up the CEO?
Yes. For SEV0, executive leadership should be notified immediately (via Comms Lead).
What is the SLA?
Immediate response (MTTA < 5 mins). Resolution as fast as humanly possible.

Learn More

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