Amazon RDS - what is the concurrent snapshot copy limit in ONE region

In your use case, where snapshots are shared across multiple accounts in the same Region, each account would still adhere to the same concurrent limit of 20 snapshot copy requests in progress. This limit is enforced per account, regardless of whether the snapshots are being copied within the same Region or across different Regions. If you anticipate exceeding this limit due to the volume of snapshots, considering below:

1. Stagger Snapshot Copies: Distribute the snapshot copy requests across different times to avoid hitting the concurrent limit.
2. Automate with AWS CLI or SDK: Set up automation to monitor and queue snapshot copy requests, ensuring they don't exceed the limit.
3. Explore Sharing Alternatives: If sharing snapshots among multiple accounts is the goal, consider using AWS Resource Access Manager (RAM) to grant access to shared snapshots directly, rather than copying them.

The 20‑snapshot concurrent copy limit documented for Amazon RDS applies only to cross‑Region snapshot copies. Within the same Region, there isn’t a published hard limit on concurrent snapshot copies, but throughput and I/O capacity on the underlying storage can still constrain how many copies progress at once. In‑Region snapshot copies are treated as standard snapshot creation operations, and RDS queues or throttles them automatically if internal service capacity is reached. In practice, you can initiate multiple in‑Region snapshot copies simultaneously, but performance may degrade if many large snapshots start at once. —Taz