Today's (June 20) downtime explained: Root cause and next steps
On June 20, Cal.com experienced a 30 minute outage due to a surge in embed traffic. Learn what happened, how we responded, and the steps we’re taking to prevent it in the future.
At Cal.com, we take platform reliability seriously. We want to share a brief update regarding a recent outage and the steps we’re taking to prevent similar incidents in the future.
What happened?
Earlier today, our infrastructure experienced an unexpected traffic surge. Over 1.44 million requests were made to a newly built prefetch embed endpoint within a very short timeframe. These requests originated from a customer who was prerendering our embed script on every page load across a high-traffic site. As a result, our systems were briefly overwhelmed, which caused degraded performance and availability issues for some users.
What we’re doing about it
To immediately stabilize the platform, our engineering team acted quickly to mitigate the overload and restore normal service. We have also prepared a fix to prevent this from happening again. A pull request introducing rate limiting on the embed endpoint is ready to be shipped.
This update will help us absorb traffic spikes more effectively, maintain availability for all users, and ensure that embeds function correctly even under heavy load.
Our commitment
We know that Cal.com is a critical part of your workflow. Whether you use our platform to schedule demos, meetings, interviews, or anything else, we understand the importance of uptime and reliability.
We remain committed to continuous improvement and transparency. This incident revealed a gap in our rate-limiting strategy, and we are already taking action to address it.
Thank you
We appreciate your patience and trust while we worked to resolve the issue. If you have any questions or are experiencing ongoing problems, please contact us at [email protected].
The Cal.com Team
