Deployment

Readonly replica mode

featureflags can serve a second datacenter from a readonly Postgres replica of the master database. Set in the server config:

readonly: true

In this mode the http server skips every client-triggered write:

  • POST /flags/load does not register new projects/flags/variables/values and does not update report timestamps.

  • Flags unknown to the replica are absent from responses; clients fall back to their in-code defaults — no client-side changes are needed.

  • A project that has not been replicated yet is served as an empty state with version: 0 instead of an error.

New flags reach readonly clients through the master: the same app deployed in the master datacenter registers them, the rows replicate, and the first configuration change in the admin UI bumps the project version, which triggers the clients’ normal sync.

Limitations:

  • “Last reported” timestamps reflect only the traffic of the master datacenter.

  • The admin web UI is not covered by readonly and should be deployed only against the master database.