Varnish Software Blog

How to Accelerate GitHub and Reduce CI/CD Bottlenecks at Scale

Written by Adrian Herrera | 4/27/26 7:00 AM

GitHub is under more pressure than ever, and the issue isn’t just growth. It’s the way modern development systems generate traffic. GitHub has acknowledged that recent instability occurred during periods of “extremely rapid usage growth,” driven by load spikes, architectural coupling, and difficulty shedding excess traffic (see GitHub’s own post on recent availability issues). 

In one incident, two client applications unintentionally generated a more-than-tenfold increase in read traffic, contributing to backend overload. At the same time, GitHub’s availability reporting continues to show a pattern of disruption across Actions, pull requests, and core workflows.

If you are looking for ways to accelerate GitHub, improve GitHub Actions performance, or reduce CI/CD bottlenecks, the root issue is not simply scale. It is traffic shape.

Why GitHub Performance Degrades at Scale

GitHub is no longer primarily serving developers. It is serving machines.

CI/CD pipelines, self-hosted runners, dependency managers, and increasingly AI-driven workflows generate continuous, high-frequency traffic that fundamentally changes how GitHub is used. What used to be human-driven interaction has become machine-to-machine activity at scale.

The challenge is not a single large request but the relentless repetition of identical ones.

Across modern environments, repositories are cloned thousands of times across runners and regions, dependencies and packages are downloaded repeatedly, Git LFS objects are fetched over and over again, and build systems request identical artifacts across parallel jobs. Over time, this creates sustained pressure on GitHub that leads to slower builds, rate limiting, and instability.

What Large Engineering Teams Are Seeing

In large engineering environments, this pattern is already well understood. Teams are not dealing with a single bottleneck but rather systemic behavior across Git, CI, and artifact distribution. Repeated read traffic has become the dominant issue, with default branches fetched continuously across CI workers, dependencies and containers pulled repeatedly across regions, and Git LFS content duplicated across pipelines and teams.

To manage this, many organizations have started treating GitHub as a constrained resource rather than an infinitely scalable system. Even modest reductions in backend load can have outsized impact. In practice, reducing redundant traffic by just 20 to 25 percent is often enough to stabilize performance during peak CI activity. Despite this, most teams still attempt to solve the problem by adding more runners or scaling infrastructure, which increases capacity but does nothing to eliminate redundant work.

And even organizations that have their own on-premise GitHub Enterprise server aren’t spared from scalability issues: despite not having to share resources with other tenants, the scale at which machine-to-machine operations increases within their organizations, makes self-hosted GitHub Enterprise setups a constrained resource.

The Real Fix: Reduce Repetitive GitHub Traffic

The most effective way to accelerate GitHub is not to scale its underlying infrastructure, but to send it fewer requests. This is where Varnish Virtual Registry (Orca) changes the equation.

Orca introduces a caching and routing layer in front of GitHub, GitHub Packages, artifact repositories, and dependency sources. Instead of every CI job, runner, and developer system independently hitting upstream systems, repeated requests are served locally whenever possible. This fundamentally changes the load profile, ensuring that if thousands of systems request the same data, the backend only processes it once.

For teams evaluating this approach, the fastest way to understand how Orca works in practice is to start with the getting started guide or review a working example in this short walkthrough video

Where GitHub Acceleration Delivers the Most Impact

Not all GitHub traffic behaves the same, and the largest gains come from eliminating repetition in the most expensive and frequently requested operations.

In Git workflows, for example, packfile generation is compute-intensive and often repeated across CI systems. When multiple runners clone or fetch the same repository state, GitHub performs the same work repeatedly. By placing Orca in front of GitHub, identical Git requests can be served once and reused across runners, regions, and pipelines. This reduces backend load and accelerates build times without requiring any changes to developer workflows. A deeper technical explanation of this approach is available here.

GitHub LFS introduces an even larger multiplier. Large binary assets are fetched repeatedly across CI systems and often across regions and clouds. Because these objects are content-addressed, they are highly cacheable. In large-scale environments, this is already a proven pattern, with teams using Varnish in front of GitHub to cache and distribute GitHub LFS content, dramatically reducing repeated downloads and backend load while improving performance for globally distributed CI systems.

Dependencies and packages are another major source of redundant traffic. Package managers like npm, PyPI, and Maven repeatedly download the same versions across builds, environments, and teams. The same applies to Docker images, Helm charts, OS packages, and artifacts stored in systems like GitHub Packages or JFrog Artifactory. Orca acts as a shared caching layer across all of these systems, eliminating repeated upstream requests and significantly reducing build times.

Quantifying the Impact of GitHub Acceleration

When teams introduce Varnish Virtual Registry (Orca) in front of GitHub and their artifact systems, the change is immediate and visible. What used to be thousands of identical requests hitting upstream systems collapses into a much smaller set of cacheable operations. Instead of GitHub, package registries, and artifact stores doing the same work over and over again, that work is done once and reused across the entire environment. The result is not just incremental improvement, but a meaningful shift in how CI/CD systems behave under load.

Across large-scale deployments, this consistently translates into:

  • 80–95% reduction in artifact and dependency latency
  • 40–50% faster dependency resolution and build times
  • ~90% reduction in repeated backend requests
  • Reduced pressure on GitHub during peak CI activity
  • 50% or more reduction in repository and artifact system load
  • Meaningful reductions in egress and cross-region traffic costs

For globally distributed teams, the impact is even more pronounced. Requests that previously traversed regions or clouds are served locally, often reducing response times by an order of magnitude. The outcome is not just faster pipelines, but more stable CI/CD systems and far more predictable performance at scale.

GitHub Actions: The Multiplier Effect

GitHub Actions amplifies both the problem and the opportunity.

Each runner independently retrieves source code, dependencies, and artifacts, creating a dense layer of redundant traffic across Git, package registries, and artifact systems.

In self-hosted GitHub Actions environments, Orca can sit in front of these systems and absorb repeated read traffic without requiring any changes to existing workflows. Instead of thousands of runners repeatedly fetching the same content from GitHub, GitHub Packages, or upstream registries, requests are served locally whenever possible. This leads to faster builds, fewer failures under load, reduced backend strain, and more predictable CI/CD performance during spikes.

The Architectural Shift

GitHub remains the system of record, but the way teams interact with it is evolving. Rather than sending every request directly to GitHub, organizations are introducing Orca as a control layer that absorbs repeated traffic, reduces backend load, and smooths spikes from CI/CD and machine-driven workflows. This approach allows teams to scale GitHub usage without proportionally scaling infrastructure.

Get Started with Varnish Virtual Registry (Orca)

If you are experiencing slow builds, GitHub rate pressure, or rising CI/CD infrastructure costs, the fastest way to see impact is to introduce Orca into your request path and observe the difference. You can get started in minutes by following the quickstart guide or watch how it works in practice.

GitHub does not need to work harder. It needs to work less. Accelerating GitHub is not about adding more infrastructure, but about eliminating redundant work, localizing access, and controlling how code and artifacts move through your environment.