Dyno Isolation
Last updated October 16, 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
Performance and Private dynos don’t share the underlying compute instance with other dynos. These dyno types are not only more powerful, but also experience low variability in performance. In addition to dedicated compute resources, Private and Shield dynos are even more isolated by their own virtual network of the space they’re in.
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.