Vercel Global Config

A Global Config is a global data store that enables experimentation with feature flags, A/B testing, critical redirects, and IP blocking. It enables you to read data in the region closest to the user without querying an external database or hitting upstream servers.

Global Config is optimized for frequent reads, which typically complete in less than a millisecond on Vercel. Read latency depends on your application's usage patterns.

You can use a Global Config in Middleware and Vercel Functions.

Vercel actively replicates Global Config alongside your function's code, so even cold starts can read the latest replicated configuration without a network request. Reading configuration that's already available locally is instant.

Global Config uses active cache invalidation. Vercel injects the configuration version into a request header, so your function can immediately determine whether its local data is current for that request.

When the header identifies a newer version, Global Config serves the local value and fetches the update in the background. If the local version is too far behind, the read becomes blocking.

This gives you the ideal balance of local read speed and global update propagation.

Your application's observed read latency depends on its usage patterns:

• How many functions read the config.
• How reads are distributed over time.
• How reads are distributed geographically.
• How often the config changes.

The Vercel documentation site uses Global Config in production. It reads Global Config for every request, globally, with the following observed read latencies:

P50 is the median: half of reads complete at or below that latency. P75 and p99 are the 75th and 99th percentiles: 75% and 99% of reads in a measurement complete at or below those latencies, respectively. About 0.1% of reads in this workload involved cold starts.

These measurements reflect this application's traffic and configuration update patterns, rather than a latency guarantee for every workload. Measure your own reads with representative traffic, including cold starts and configuration updates, to understand your application's latency.

Global Configs are great for data that is accessed frequently and updated infrequently. Here are some examples of storage data suitable for Global Config:

You can create and manage your Global Config from either Vercel REST API or Dashboard. You can scope your Global Configs to your Hobby team or team, and connect them to as many projects as you want.

To get started, see our quickstart.

If you'd like to know whether or not Global Config can be integrated into your workflow, it's worth knowing the following:

• You can have one or more Global Configs per Vercel account, depending on your plan as explained in Limits
• You can use multiple Global Configs in one Vercel project
• Each Global Config can be accessed by multiple Vercel projects
• Global Configs can be scoped to different environments within projects using environment variables
• Global Config access is secure by default. A read access token is required to read from them, and an API token is required to write to them

See our Global Config limits docs to learn more

There are alternative solutions to Global Config for handling A/B testing, feature flags, and IP blocking. The following table lays out how those solutions compare to Global Config:

To learn about Global Config limits and pricing, see our Global Config limits docs.

• Quickstart
• Read with the SDK
• Use the Dashboard
• Manage with the API
• Global Config Limits