Which of the following will resolve this issue?

Explanations:

Increasingmax_connectionswould raise the limit on simultaneous connections allowed to the database. However, this does not address the root cause, which is likely Lambda functions overwhelming the DB cluster’s ability to handle concurrent connections, leading to throttling and connection errors.

Increasing the instance size of the DB cluster would provide more resources (CPU, memory) to handle increased concurrent connections and queries. This is the most effective solution for scaling to handle a large number of concurrent Lambda invocations.

Changing the DB cluster to Multi-AZ improves availability and failover capabilities but does not address the issue of insufficient connections or the ability to handle a high volume of concurrent Lambda requests.

Increasing the number of Aurora Replicas helps with read scalability, not with the overall ability to handle concurrent writes or manage connection limits on the primary instance, which is the issue in this case.