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While load testing our user creation code path in production, we identified that executing the DB statement to update the `Group#user_count` column within a transaction is creating a bottleneck for us. This is because the creation of a user and addition of the user to the relevant groups are done in a transaction. When we execute the DB statement to update `Group#user_count` for the relevant group, a row level lock is held until the transaction completes. This row level lock acts like a global lock when the server is creating users that will be added to the same group in quick succession. Instead of updating the counter cache within a transaction which the default ActiveRecord `counter_cache` option does, we simply update the counter cache outside of the committing transaction. Co-authored-by: Rafael dos Santos Silva <xfalcox@gmail.com> Co-authored-by: Rafael dos Santos Silva <xfalcox@gmail.com>