Docs · Configure
Sleeping, always-on and sizes
An app goes to sleep after 5 minutes without traffic and wakes on the next request, which waits for it instead of failing. You pay for compute only while it is awake. On paid plans you can keep an app always on instead.
How sleeping works
- An app with no connections for 5 minutes is stopped. The idle time is not configurable.
- The next request starts it again. The request is held until your app is listening on its port, then answered. It is not dropped and not answered with an error page.
- A small binary is usually back in about a second. How long yours takes depends on how fast it starts: a Go binary that listens at once is quickest, an app that warms a cache or connects to a database before listening is slower. While it wakes, it gets a full CPU core for a few seconds.
- If an app is not listening 30 seconds after it was woken, the request fails.
- Static sites never sleep. Nothing runs: their files are served directly, and they have no size.
Your app’s Usage tab shows when it was awake and asleep. A sleeping app is not billed; see Plans, usage and billing.
Always on
Tick Always on in the app’s Settings → Resources (or in Size when you create it) and the app never sleeps, so no visitor waits for a wake. It is billed for every hour it runs.
- Always on is on Starter, Growth and Business. On Free, apps always sleep when idle.
- New apps start with it off. A new environment copies production’s size but sleeps when idle.
- Extra processes, such as a queue worker, need the app to be always on.
Sizes
Each app has a memory size and a CPU limit, chosen separately in Settings → Resources. CPU is the most of one core the app may use. Saving restarts the app at the new size; nothing is rebuilt. New apps start at 256 MB and 25% CPU.
| Plan | Memory | CPU | Always on |
|---|---|---|---|
| Free | 256 MB | 25% of a core | No |
| Starter | 512 MB | 50% of a core | Yes |
| Growth | 2 GB | 2 cores | Yes |
| Business | 8 GB | 4 cores | Yes |
The dashboard offers 256 MB, 512 MB, 1 GB, 2 GB, 4 GB and 8 GB of memory and 25%, 50%, 100%, 200% and 400% of a core, up to your plan’s largest. Sizes above your plan are shown but cannot be picked, each marked with the plan that has it (“on Growth”, “on Business”).
What a size costs
Compute is billed per GB-hour awake: memory in GB multiplied by hours awake, at $0.015 per GB-hour. CPU is included. A 512 MB app awake for 100 hours in a month uses 50 GB-hours, which is $0.75. The same app always on for a 730-hour month is 365 GB-hours, $5.48.
If your plan changes
On a smaller plan, sizes above its limit are reduced to it, Always on is turned off where the plan has none, and apps beyond the plan’s app count are paused, newest first. A paused app shows paused: past the plan's apps.