GoKawiilI wanted to give an update on GitHub’s availability in light of two recent incidents. Both of those incidents are not acceptable, and we are sorry for the impact they had on you. I wanted to share some details on them, as well as explain what we’ve done and what we’re doing to improve our reliability.
We started executing our plan to increase GitHub’s capacity by 10X in October 2025 with a goal of substantially improving reliability and failover. By February 2026, it was clear that we needed to design for a future that requires 30X today’s scale.
The main driver is a rapid change in how software is being built. Since the second half of December 2025, agentic development workflows have accelerated sharply. By nearly every measure, the direction is already clear: repository creation, pull request activity, API usage, automation, and large-repository workloads are all growing quickly.
This exponential growth does not stress one system at a time. A pull request can touch Git storage, mergeability checks, branch protection, GitHub Actions, search, notifications, permissions, webhooks, APIs, background jobs, caches, and databases. At high scale, small inefficiencies compound: queues deepen, cache misses become database load, indexes fall behind, retries amplify traffic, and one slow dependency can affect several product experiences.
Our priorities are clear: availability first, then capacity, then new features. We are reducing unnecessary work, improving caching, isolating critical services, removing single points of failure, and moving performance-sensitive paths into systems designed for these workloads. This is distributed systems work: reducing hidden coupling, limiting blast radius, and making GitHub degrade gracefully when one subsystem is under pressure. We’re making progress quickly, but these incidents are examples of where there’s still work to do.
What we’re doing
Short term, we had to resolve a variety of bottlenecks that appeared faster than expected from moving webhooks to a different backend (out of MySQL), redesigning user session cache to redoing authentication and authorization flows to substantially reduce database load. We also leveraged our migration to Azure to stand up a lot more compute.
Next we focused on isolating critical services like git and GitHub Actions from other workloads and minimizing the blast radius by minimizing single points of failure. This work started with careful analysis of dependencies and different tiers of traffic to understand what needs to be pulled apart and how we can minimize impact on legitimate traffic from various attacks. Then we addressed those in order of risk. Similarly, we accelerated parts of migrating performance or scale sensitive code out of Ruby monolith into Go.
While we were already in progress of migrating out of our smaller custom data centers into public cloud, we started working on path to multi cloud. This longer-term measure is necessary to achieve the level of resilience, low latency, and flexibility that will be needed in the future.
The number of repositories on GitHub is growing faster than ever, but a much harder scaling challenge is the rise of large monorepos. For the last three months, we’ve been investing heavily in response to this trend both within git system and in the pull request experience.
... continue reading