When enabling grant-set storage scheme in AM (Configure>Global Services>OAuth2 Provider>CTS Storage Scheme), this can cause CTS performance issues when there are high volumes of tokens issued via client credential grant.
With client credential grant, all tokens for a single OAuth2 client will be added to a single grant set entry in CTS, because the subject and client are the same entity. E.g. the multiple coreTokenMultiString03 entries in the following grantset
The coreTokenExpirationDate is updated for each token added: when there is a steady flow of tokens, this means that the grantset will keep growing without being reaped. This in turn causes performance issues and replication delays in CTS.