ShotGrid REST API v5 and v6 concurrent requests during application migration

A small application needs to move from ShotGrid REST API v5 to v6 without an outage. The migration plan relies on the documented ability to address different major versions in the same environment and on OAuth2 token refresh to keep authentication active while the client configuration changes.

The integration boundary is between the ShotGrid REST API versioning surface and the application’s client configuration and token management. The platform publishes a deprecation window for older major versions after a new major version release, and version selection is described as possible via URL path and an X-Api-Version header. OAuth2 refresh tokens can be used to obtain new access tokens while requests continue. There is no built-in cut-over feature, so the switch of endpoint or version must be orchestrated by the client.

Uncertainty remains about production use of concurrent versions and the operational decisions required for a zero-downtime change. Rate limits are described as applied per API version, and data consistency between a local cache and ShotGrid during a version switch is not guaranteed.

Is concurrent use of v5 and v6 via the X-Api-Version header supported for production traffic during a migration window? What decision criteria should govern the timing of a client configuration switch given that deprecation timelines may shift? How are rate limits accounted for when the same application issues requests to both versions?