---
title: Investigate latency issues and slowness on Vercel
description: Learn how to use Observability to investigate latency issues and slowness on Vercel.
url: "https://vercel.com/kb/guide/investigate-latency-issues-and-slowness"
published: 2025-11-03
last_updated: 2025-11-11
authors: DX Team
install_vercel_plugin: npx plugins add vercel/vercel-plugin
---

**Problem**: One of your functions is timing out, not serving responses quickly enough, or otherwise alerting.

You can use [Observability](/docs/observability) to investigate and understand slow responses from your functions and its effects on function duration, error rates, and consumption. To do so:

1. From your [dashboard](/dashboard), select the project you want to investigate.
   
2. Navigate from your dashboard to the **Observability** tab.
   
3. Choose **External APIs** and set an appropriate time range filter (e.g. last 6 hours).
   
4. From the list, sort by **P75 duration** to find hosts with the slowest response times, e.g. `mycms.com`: {' '}
   
   ![sort-by-p75-light.png](https://images.ctfassets.net/hjgychtc108g/4ctc1dPPUprSiLWh3fIpRn/f10681c36ad3d839c97ddda1c438eff0/sort-by-p75-light.png)
   
   Media
   
5. Select the hostname with high duration or error rate: {' '}
   
   ![select-hostname-light.png](https://images.ctfassets.net/hjgychtc108g/4TAdIfpNSODOuTeHP1AVxX/4321715cee08a539cbf3760d3dd77599/select-hostname-light.png)
   
   Media
   
6. You can see a distribution of requests over time, as well as their latency. When selecting Functions, you can see which of your function routes sent the requests to the slow external API and navigate to the appropriate view right away.
   

## More resources

- [Observability overview](/docs/observability)
  
- [Observability limits and pricing](/docs/observability/limits-and-pricing)

## More Observability guides

- [How to control AI provider data handling with AI Gateway](/kb/guide/control-ai-provider-data): Prevent AI providers from training on your prompts, enforce zero data retention, and restrict providers and models with Vercel AI Gateway.
- [Troubleshooting Build Error: "Build step did not complete within the maximum of 45 minutes"](/kb/guide/troubleshooting-build-error-build-step-did-not-complete-within-45-minutes): Learn common reasons Vercel builds hit the 45-minute limit and how to reduce build times so your deployments stay fast and reliable.
- [Troubleshooting Builds Failing with SIGKILL or Out of Memory Errors](/kb/guide/troubleshooting-sigkill-out-of-memory-errors): Learn how to troubleshoot builds failing with SIGKILL or Out of Memory errors on a Vercel Deployment.