Up to 1TB. I recall a very recent post in restic forums from someone with a 100 TB repo! No issue with RAM usage. Also Restic runs much faster since 1.12, RAM

Up to 1TB. I recall a very recent post in restic forums from someone with a 100 TB repo! No issue with RAM usage. Also Restic runs much faster since 1.12, RAM usage is now more limited in time duration. I don’t have first hand experience with larger repositories.