# Which Problems Are Solved
Milestones used existing events from a number of aggregates. OIDC
session is one of them. We noticed in load-tests that the reduction of
the oidc_session.added event into the milestone projection is a costly
business with payload based conditionals. A milestone is reached once,
but even then we remain subscribed to the OIDC events. This requires the
projections.current_states to be updated continuously.
# How the Problems Are Solved
The milestone creation is refactored to use dedicated events instead.
The command side decides when a milestone is reached and creates the
reached event once for each milestone when required.
# Additional Changes
In order to prevent reached milestones being created twice, a migration
script is provided. When the old `projections.milestones` table exist,
the state is read from there and `v2` milestone aggregate events are
created, with the original reached and pushed dates.
# Additional Context
- Closes https://github.com/zitadel/zitadel/issues/8800
This implementation increases parallel write capabilities of the eventstore.
Please have a look at the technical advisories: [05](https://zitadel.com/docs/support/advisory/a10005) and [06](https://zitadel.com/docs/support/advisory/a10006).
The implementation of eventstore.push is rewritten and stored events are migrated to a new table `eventstore.events2`.
If you are using cockroach: make sure that the database user of ZITADEL has `VIEWACTIVITY` grant. This is used to query events.
Tim MöhlmannandGitHub
SilvanandGitHub
Stefan BenzandGitHub