Amazon ElastiCache Serverless now supports same-slot WATCH command

Today, we are announcing that [Amazon ElastiCache Serverless](https://aws.amazon.com/elasticache/) now supports the WATCH command for same-slot transactions, helping developers build more reliable applications with improved data consistency in high-concurrency scenarios. With this launch, the WATCH command makes transactions conditional, ensuring they execute only when monitored keys remain unchanged. For ElastiCache Serverless, the WATCH command works with transactions that operate on keys within the same hash slot as the watched keys. When applications attempt to watch keys that are not in the same hash slot, they'll receive a CROSSSLOT error. Developers can control key placement by using hash tags in their key names to ensure keys hash to the same slot. The transaction will also be aborted when ElastiCache Serverless cannot guarantee the state of watched keys. WATCH command support is available in all AWS regions where ElastiCache Serverless is supported at no additional cost. To get started, create transactions using the WATCH command through your preferred client library. To learn more about conditional transactions and the WATCH command, see the [ElastiCache Serverless documentation](https://docs.aws.amazon.com/AmazonElastiCache/latest/dg/serverless.html), and the Valkey [transactions documentation](https://valkey.io/topics/transactions/).