Dyno Isolation
Last updated December 03, 2024
This article describes how dynos are isolated on Heroku.
Shared Compute
Eco, Basic and Standard dynos, while completely isolated, share an underlying compute instance with other dynos. Heroku employs several techniques to ensure fair use of the underlying resources. These dyno types can experience a degree of performance variability depending on the total load on the underlying instance.
Dedicated Compute
Our Performance, Private, Shield, and Fir dyno tiers don’t share their underlying compute instance with others dynos belonging to an app. This allows for a lower variability in dyno performance.
In addition to dedicated compute resources, Private, Shield, and Fir dynos have their own virtual networking layer of the space they belong to.
Ephemeral Filesystem
Each dyno gets its own ephemeral filesystem, with a fresh copy of the most recently deployed code. During the dyno’s lifetime, its running processes can use the filesystem as a temporary scratchpad, but no files that are written are visible to processes in any other dyno. Any files written get discarded the moment the dyno stops or restarts, including automatic restarts.