# Cold Starts in Deployment: What They Are and How to Fix Them

> Cold starts make your app slow on the first request. Learn why Railway, Render, and Vercel cause cold starts and how to fix the problem for good in 2026.
- **Author**: harsh-kanani
- **Published**: 2026-06-17
- **Modified**: 2026-06-17
- **Category**: Deployment Guides
- **URL**: https://kuberns.com/blogs/cold-start-problem-deployment/

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Cold starts happen when your app container is spun down after inactivity and has to reinitialise before it can respond to the next request. Depending on the platform and your app's bundle size, that can add anywhere from 1 second to over 30 seconds of latency to the first hit.

If you are on Render's free tier, Vercel's serverless backend, or Railway's free plan, you have almost certainly run into this. Your app feels snappy after the first request but makes the first user wait. In production, that is a real problem.

This guide covers exactly what the cold start problem is, which platforms cause it and why, what the workarounds are, and how [Kuberns](https://dashboard.kuberns.com) eliminates it by default using always-on containers.

## What Is the Cold Start Problem in Deployment?

![Cold start problem explained: what happens when a container spins down and wakes](https://kuberns-blogs.s3.ap-south-1.amazonaws.com/cold-start-problem-explained.png)

A cold start is what happens when a cloud platform shuts down your app's container or function after a period of inactivity to save resources. When the next request arrives, the platform has to spin the environment back up before your code can run.

This reinitialisation involves:

- Provisioning or reactivating a container or execution environment
- Loading your app's runtime and dependencies
- Running any initialisation code in your application

Only after all of that is complete does your app actually handle the request. For users, it looks like the app is hanging. For APIs, clients see timeouts or extremely slow responses.

The issue is particularly painful for:

- Backend APIs where first-request latency breaks the user experience
- Scheduled jobs that trigger infrequently and always hit a cold container
- Apps with heavy initialisation (database connections, loading models, parsing config)

This is a distinct problem from general deployment slowness. If you are seeing consistently slow first requests but fast subsequent ones, it is almost certainly a cold start. If your app is slow across the board, check [why your deployment might be slow for other reasons](/blogs/why-is-my-deployment-slow/).

## Which Platforms Have Cold Start Problems?

![Cold start comparison across Render, Vercel, Railway and Fly.io](https://kuberns-blogs.s3.ap-south-1.amazonaws.com/cold-start-platforms-comparison.png)

Cold starts are not a universal problem. They are a specific consequence of how certain platforms manage idle resources. Here is how the most popular deployment platforms handle it.

| Platform | Cold start risk | When it triggers | Workaround |
|---|---|---|---|
| Render (free) | High | After 15 min idle | Upgrade to paid or use ping service |
| Vercel (serverless) | Medium | Every new function invocation | Use Edge Functions or avoid backend on Vercel |
| Railway (free) | Medium | After inactivity on free plan | Upgrade to Hobby plan |
| Fly.io (scaled to zero) | Medium | When scaled to zero replicas | Set min replicas to 1 |
| Kuberns | None | Never | Always-on containers by default |

### Render

Render's free tier spins down web services after 15 minutes without inbound traffic. This is documented behaviour. When a request comes in after spin-down, Render restarts the service, a process that takes approximately 60 seconds. Render even shows a loading page to the user while the service wakes up.

This is not a bug. It is how Render's free tier works to manage infrastructure costs. On paid plans starting at $7/month, services stay alive. But it means free-tier Render is unsuitable for any production app where first-request latency matters.

> Thinking about using Render for a real production workload? Read [whether Render is actually good for production](/blogs/is-render-good-for-production/) before committing.

### Vercel

Vercel is built around serverless functions. Every backend API route on Vercel runs as a serverless function that is provisioned on demand. When no warm instance is available, the function cold starts. This typically adds 200ms to over 1 second depending on your bundle size and runtime.

Vercel is optimised for frontend delivery and edge functions. It is not designed to run persistent backend processes. Teams trying to run a Node.js API or a full-stack app with heavy server logic frequently hit cold start issues, especially at low traffic volumes.

> Before deploying your Node.js backend on Vercel, read [what actually works and what breaks with Node.js on Vercel](/blogs/vercel-node-js/).

### Railway

Railway's free tier allows services to sleep when they receive no traffic. Like Render, this is a cost management measure on the free plan. On Railway's Hobby plan ($5/month), services run persistent containers that do not cold start in the same way as serverless platforms.

Railway's cold start is less severe than Render's, typically 10 to 30 seconds rather than 60, but it is still a production issue for any app with intermittent traffic patterns.

> If you are evaluating Railway for a serious project, read [whether Railway is reliable for production workloads](/blogs/is-railway-good-for-production/) first.

### Fly.io

Fly.io supports scaling services to zero replicas, which is where cold starts occur. When traffic arrives and no replica is running, Fly provisions a new one. The latency depends on your app's startup time. Teams using Fly.io for production typically set a minimum replica count of 1 to avoid this, which adds cost.

> See a full breakdown of [whether Fly.io is a good fit for production](/blogs/is-fly-io-good-for-production/) before building on it.

## How to Fix Cold Starts: Workarounds Per Platform

![Platform workarounds for cold starts: pinging, upgrading plans, and edge functions](https://kuberns-blogs.s3.ap-south-1.amazonaws.com/cold-start-workarounds.png)

If you are already on one of these platforms and cannot switch immediately, here are the practical workarounds.

**Render: ping to prevent spin-down**

Set up a free monitoring service like UptimeRobot to send an HTTP request to your app every 14 minutes. This prevents Render from triggering the spin-down. It works but it is maintenance overhead and will not help if your app restarts for any other reason.

**Render and Railway: upgrade to a paid plan**

The cleanest fix on both platforms is upgrading. Render's paid instances ($7/month) stay live. Railway's Hobby plan ($5/month) runs persistent containers. If you are in production, this is the minimum baseline.

**Vercel: use Edge Functions for latency-sensitive routes**

Vercel's Edge Runtime has lower cold start latency than Node.js serverless functions because it uses V8 isolates instead of containers. For simple API routes, this can reduce cold start from 1 second to under 50ms. But Edge Functions have significant limitations: no Node.js APIs, no filesystem access, limited package support.

**General: minimise initialisation work**

Reduce cold start duration by cutting what your app does at startup. Lazy-load database connections, defer non-critical setup, and reduce bundle size. This does not eliminate cold starts but shortens them.

These are all workarounds. None of them change the underlying architecture. For [zero-downtime production deployments](/blogs/zero-downtime-deployment/) that never make users wait, the real answer is a platform that never spins down in the first place.

## How to Deploy on Kuberns and Eliminate Cold Starts

![Deploying on Kuberns to eliminate cold starts with always-on AWS containers](https://kuberns-blogs.s3.ap-south-1.amazonaws.com/kuberns-always-on-containers.png)

[Kuberns](https://dashboard.kuberns.com) runs every application in always-on containers on AWS infrastructure. There is no sleep mode, no spin-down on idle, and no cold start on any request. The first request is as fast as the thousandth.

### Always-On Containers by Default

Every app deployed on Kuberns runs in a persistent container that stays live regardless of traffic volume. You do not need to configure anything, upgrade to a special plan, or set minimum replicas. This is simply how Kuberns works: containers are always running, always warm.

This is architecturally different from serverless functions (which are provisioned on demand) and spin-down free tiers (which kill idle containers to save costs). Kuberns handles the cost optimisation on the infrastructure side so you do not have to choose between saving money and staying warm.

### Connect Your Repo and Deploy in Under 5 Minutes

Getting your app onto Kuberns takes three steps:

1. Connect your GitHub repository to [Kuberns](https://dashboard.kuberns.com)
2. Set your environment variables in the dashboard
3. Click deploy, Kuberns auto-detects your stack, builds, and goes live

No Dockerfiles. No YAML. No build configuration. Your app is running on AWS-backed always-on containers in under five minutes. For a full walkthrough, see [the fastest way to deploy a web app in 2026](/blogs/fastest-way-to-deploy-web-app/).

### Your App Stays Live Even at Zero Traffic

Even when no one is using your app, Kuberns keeps the container running. You do not need ping services, uptime monitors hacking around spin-down timers, or paid plan upgrades just to keep your app warm overnight.

This matters for APIs, background services, scheduled jobs, and any app where the first user of the day should not wait 60 seconds for a response. If you are comparing platforms for a team project, see [the best deployment platforms for small dev teams in 2026](/blogs/best-deployment-platform-small-dev-teams/) for the full picture.

[![Deploy without cold starts on Kuberns](https://kuberns-blogs.s3.ap-south-1.amazonaws.com/deploy-on-kuberns-bannner6.png)](https://dashboard.kuberns.com)

> Want to compare Kuberns against Railway and Render directly? Read the full [Railway vs Render vs Kuberns comparison](/blogs/railway-vs-render-vs-kuberns/) to see how they stack up across pricing, reliability, and cold start behaviour.

## Conclusion

Cold starts are not a minor inconvenience. In production, a 30-second delay on the first request loses users, breaks API integrations, and undermines trust in your application. Render's spin-down, Vercel's serverless model, and Railway's free-tier sleep are all real cold start triggers that affect real production apps.

The workarounds help, but they are patches. The actual solution is deploying on a platform that runs always-on containers and never puts your app to sleep. That is what [Kuberns](https://dashboard.kuberns.com) does by default, on AWS infrastructure, without any additional configuration.

[![Start deploying on Kuberns with no cold starts](https://kuberns-blogs.s3.ap-south-1.amazonaws.com/CTA_banner.png)](https://dashboard.kuberns.com)

## FAQ

**What is the cold start problem in deployment?**

The cold start problem happens when a cloud platform spins down your app after inactivity. The next request has to wait while the container or function reinitialises, causing latency from 1 second to over 30 seconds.

**Why is my app slow on the first request?**

If your app is consistently slow on the first request but fast afterwards, you are almost certainly experiencing a cold start. This happens on platforms that spin down idle services, including Render free tier, Vercel serverless functions, and Railway free plans.

**Does Render have cold start problems?**

Yes. Render spins down free tier web services after 15 minutes of inactivity. Restarting takes approximately 60 seconds. Upgrading to a paid plan prevents spin-down.

**Does Vercel have cold starts?**

Yes. Vercel uses serverless functions for backend code, which cold start on each new invocation when no warm instance is available. Vercel is optimised for frontend and edge delivery, not persistent backend processes.

**Does Railway have cold start issues?**

Railway free tier services sleep after inactivity. On paid plans, Railway runs persistent containers that do not cold start in the same way as serverless platforms.

**What is the best fix for cold starts in production?**

The most reliable fix is a platform that runs always-on containers that never spin down. Kuberns runs your app on persistent AWS containers by default, which means no cold start on any request including the first one.

**Can I fix cold starts by pinging my app?**

You can use UptimeRobot to ping your app every 14 minutes to prevent Render from spinning it down. This works but it is a workaround, not a fix. It does not help with serverless function cold starts on platforms like Vercel.

**What are always-on containers?**

Always-on containers are persistent runtime environments that stay active regardless of traffic. Unlike serverless functions or spin-down free tiers, they do not need to reinitialise between requests, which eliminates cold start latency entirely.

**Does Kuberns have cold starts?**

No. Kuberns runs applications in always-on containers on AWS infrastructure. There is no sleep mode, no spin-down on idle, and no cold start latency on any request.

**How long do cold starts take?**

Cold start duration depends on the platform and runtime. Render free tier takes approximately 60 seconds to wake. Vercel serverless functions cold start in 200ms to 1 second depending on bundle size. Railway free tier restarts can take 10 to 30 seconds.

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