Grafana read‑only mode limits during database migration

Goal

Determine whether enabling Grafana’s readonly_mode setting fully protects the instance from concurrent writes while the database migration scripts run, and how many HTTP requests can still be served during that period.

Constraints & Uncertainty

The official documentation states that readonly_mode = true disables UI edits but does not mention external API calls or internal cache behavior during migration. The migration phase blocks HTTP requests until completion, yet the exact request capacity and the effect on write‑heavy external services (e.g., alerting, API dashboards) remain undocumented for Grafana 9.x.

Unresolved Questions

1. Does read‑only mode prevent all external API writes (POST/PUT) to Grafana during the migration, or are certain endpoints still writable?
2. What is the maximum number of concurrent read requests that Grafana can serve while the migration scripts are executing?
3. How does the internal cache interact with read‑only mode during migration—does it cause stale data to be returned or does it block reads entirely?