> ## Documentation Index
> Fetch the complete documentation index at: https://site.aspect.build/llms.txt
> Use this file to discover all available pages before exploring further.

# Remote build execution (RBE)

> Aspect Workflows remote build execution (RBE) cluster implementing the Bazel REv2 protocol to parallelize actions across remote workers.

A local Bazel build is limited by the number of CPU cores on the machine running it. Remote Build Execution (RBE) removes that ceiling: Bazel distributes individual actions across a pool of remote workers via `--remote_executor`, so hundreds of compile and test actions run in parallel regardless of local hardware.

Every Workflows deployment includes an optional remote execution cluster that implements the [Bazel Remote Execution Protocol v2](https://docs.bazel.build/versions/2.0.0/remote-execution.html). The cluster is highly configurable: you define one or more *executors*, each pinned to a specific container image (and optionally a custom Bazel platform), and each executor backed by one or more worker pools with their own instance type (including GPU instance types), CPU/memory shape, network access toggle, max concurrency, and auto-scaling policy (minimum, warm, and maximum pool sizes; target-tracking scaling; and schedule-based rules to pre-scale ahead of known peaks). This means you can size each executor to exactly the workload it handles, mix architectures (`amd64`, `arm64`) and toolchain images within a single deployment, and scale down to zero when the queue is empty so you pay nothing for idle capacity.

## What RBE gives you

**Action-level parallelism.** Bazel's action graph is already a DAG. With RBE, every action that has no unmet dependencies runs immediately on the worker pool, not queued behind other actions on a single machine.

**Multiple platforms, your hardware.** Define several RBE platforms side by side, the same way you define runner groups: each pinned to its own container image and instance type, so you control architecture, CPU, memory, NVMe, and GPUs per platform. Docker-based tests are fully supported on workers.

**Right-sized actions.** Each platform supports multiple worker size classes, and actions are matched to a size class and memory automatically, so heavyweight link and test actions land on big machines without reserving them for every small compile.

**Per-action platform constraints.** Each action can declare the execution platform it needs. You can mix container images, OS versions, and toolchains within a single build without splitting it into separate jobs.

**Cross-platform builds.** The worker pool supports arm64 and amd64 simultaneously. Cross-compilation, multi-arch container publishing, and other cross-platform workflows run as native builds on the right architecture rather than through emulation.

**Cost-proportional resource allocation.** Provision large workers for link steps and test shards that need memory; use smaller workers for cheap compile actions. Workers scale down when the queue is empty, so you pay only for what you use.

## Standard protocol, no lock-in

The execution cluster implements the Bazel Remote Execution Protocol v2. Any REv2-compatible client works with it, and nothing about your build depends on RBE to keep working.

## Adopt at your own pace

RBE is in every Workflows deployment from day one for when you're ready for it. Most teams start with the warm [CI runners](/docs/aspect-workflows/features/ci-runners) and [remote cache](/docs/aspect-workflows/features/remote-cache), which deliver most of the speedup with no migration; turning RBE on later is a configuration change on the same deployment, tuned by Aspect engineers under our SLA.

{user.loggedIn && user.tenantMetadata?.docsGroups?.includes('workflows-subscriber') ? (
<Info>
See also:
<ul>
<li><a href="/docs/aspect-workflows/using-workflows/remote-cache-config">Remote cache configuration</a></li>
<li><a href="/docs/aspect-workflows/using-workflows/remote-execution-config">Remote execution configuration</a></li>
<li><a href="/docs/aspect-workflows/using-workflows/external-cache-config">External remote cache and execution configuration</a></li>
</ul>
</Info>
) : !user.loggedIn ? (
<Info>
To access the complete product documentation, including installation and detailed configuration, <a href="/login?redirect=%2Fdocs%2Faspect-workflows%2Ffeatures%2Fremote-execution">log in</a> with your Aspect account, or ask an Admin in your organization to invite you via the <a href="https://auth.aspect.build/oauth/portal/users">Aspect admin portal</a>.
</Info>
) : (
<Info>
If you are a Workflows customer, contact Aspect support for access to complete product documentation, including installation and detailed configuration. <br /><br />Not a customer yet? Sign up for a free 30-day trial at <a href="/trial">/trial</a> to get started.
</Info>
)}