Dyno Scaling and Process Limits
Last updated March 05, 2025
Table of Contents
The following are the limits for different Heroku dynos. For dyno features, see Dyno Tiers. For dyno specs, see Technical Specifications by Dyno Size.
Default Scaling Limits
Cedar Scaling Limits
The following limits exist per Cedar-generation app:
- By default, applications can run a total of 100 dynos across all process types.
- Apps running on Eco or Basic dynos can have only one dyno running per process type.
- Apps running on Eco dynos can have a maximum of two concurrently running dynos. For example, you can have one dyno running for your web process, and one dyno running for worker.
- You can’t scale a single process type that uses Performance, Private, or Shield dynos to more than 10 dynos.
Submit a request to raise these limits for your application.
Fir Scaling Limits
Fir, the latest generation of the Heroku platform, offers higher limits than Cedar. The following limits exist per Fir-generation app:
- By default, applications can run a total of 255 dynos across all process types.
- You can’t scale a single process type to more than 255 dynos.
Submit a request to raise these limits for your application.
Concurrent One-Off Dyno Limits
- 1 Eco one-off dyno (Eco requires a subscription to the Eco dynos plan)
- Up to 50 concurrent one-off Basic dynos
- Up to 50 concurrent one-off Standard dynos
- Up to 5 concurrent one-off Performance dynos
- Up to 5 concurrent one-off Private dynos
- Up to 5 concurrent one-off Shield dynos
- Up to 255 concurrent one-off Fir dynos
Submit a request to raise this limit for your application.
Process/Threads Limit
The maximum number of processes/threads that can exist in dynos for Cedar-generation apps depends on dyno size:
- Eco, Basic and Standard-1X dynos support no more than 256
- Standard-2X and Private-S dynos support no more than 512
- Performance-M, Private-M, Shield-M and Performance-L-RAM dynos support no more than 16384
- Performance-L, Performance-XL, Private-L and Shield-L dynos support no more than 32768
- Private-L-RAM, Shield-L-RAM and Performance-2XL dynos support no more than 65536
- Private-XL and Shield-XL dynos support no more than 131072
- Private-2XL and Shield-2XL dynos support no more than 262144
These limits include all processes and threads, whether they are executing, sleeping or in any other state. Note that the dyno counts threads and processes towards this limit. For example, a Standard-1X dyno with 255 threads and one process is at the limit, as is a dyno with 256 processes.
Fir dynos have dynamic limits for threads based on CPU and memory limits.