Preview environments
Previews that ship their settings.
Every pull request gets its own URL. The settings you change there go live with the merge.
- 1 Add the variables in the preview
- 2 Save to production
- 3 Production waits for #142
- 4 Merge: code and settings deploy together
github.com/acme/web
feature/checkout → main
Ployz · ready to mergeRequired
3 changes go live with this PR
web · Variables · not deployed yet
- STRIPE_KEYsealedPR #142
- STRIPE_WEBHOOK_SECRETsealedPR #142
- CHECKOUT_V2truePR #142
PR #142
3 changes · go live when #142 merges
Add STRIPE_KEY in the preview, save it, and production deploys it with the merged code.
Nothing left behind
Production holds the preview's changes until the pull request merges, then deploys code and settings together.
A check that blocks the merge
Make “Ployz · ready to merge” required, and GitHub waits until the changes are saved.
Its own copy of the database
Each preview gets an empty database, seeded by your setup command.
Pick what each preview copies.
Copy the database, share the cache. A shared service with data is flagged in amber, so a preview never writes to production by accident.
Previews cost RAM, not a meter.
Twenty pull requests a month with an app and a database costs $13 to $18 on Render, Railway or Heroku. On a server you already rent it's $0 until the RAM runs out. More in ephemeral environments without Kubernetes.
- Preview hours a month
- 960
- Previews running at once (average)
- 1.3
- RAM the previews need
- 2 GB
- Render preview environments$18/mo
Starter instance, $7/month for 512 MB, prorated by the second. Full-stack previews need the $25 Pro workspace.
- Heroku review apps$18/mo
Basic dyno, $7/month for 0.5 GB, prorated to the second. Essential-0 Postgres is $5.
- Railway PR environments$16/mo
Usage pricing at $10/GB RAM and $20/vCPU a month. Assumes 512 MB and 5% of a vCPU per service.
- DigitalOcean App Platform previews$13/mo
512 MiB container, $5/month, billed by the second. A dev database is $7/month.
- Your own server + Ployz$0/mo
$0 while previews fit in 4 GB of spare RAM; then a Hetzner CX33 ($9.99 + about $0.60 IPv4) per 8 GB. Ployz previews are free.
Compared with the platforms.
| What you need | Vercel, Render, Railway, Heroku | Ployz on your server |
|---|---|---|
| A preview per pull request | Yes. Render needs its Pro plan | Yes, free |
| New variable reaches production | Set it again by hand. Railway can sync environments | Saved once, deploys with the merge |
| Preview database | Fresh, on Render and Heroku | Your choice per service, seeded by a setup command |
| Cost | Billed like any running service | RAM on your own server |
Good to know.
- A save moves settings, never data.
- Previews run one replica per service.
- GitHub only for now, and no rollback yet: change a setting back and deploy.
- Ployz doesn't back up databases yet.
Questions
How do I keep environment variables in sync between preview and production?
Add the variable in the preview and click Save to production. It deploys with the merge, and a required GitHub check can block the merge until it's saved.
What is an ephemeral environment?
A short-lived copy of your app for one pull request, with its own URL and often its own database. Preview environment, review app and PR environment mean the same thing.
Do I need Kubernetes for preview environments?
No. Ployz builds each preview on Linux servers with Docker, gives it an https address and deletes it when the pull request closes.
Is there a Heroku review apps alternative?
Yes. Coolify, Dokploy and Ployz build a preview per pull request on your own server. Ployz also carries a preview's saved settings to production with the merge.
What happens to the database in a preview?
You choose. Copy it and the preview gets its own, starting empty. Share it and the preview uses production's data, flagged in amber.
What does Ployz cost?
Free on your own servers, with unlimited previews. Custom domains are $9 a month. You pay your provider for the servers.
Your servers. The whole platform. Free on your own servers.
Deploy your appFacts checked 2026-10-02.