Improve application availability and connection efficiency for Bigtable when the app profile currently uses single-cluster routing with manual failover.

Switching the Bigtable app profile to multi-cluster routing directly improves application availability and connection efficiency by enabling automatic failover and load balancing across multiple Bigtable clusters. This ensures that if one cluster becomes unavailable, traffic is automatically routed to a healthy cluster, minimizing downtime. It also distributes the read and write load, enhancing overall performance and efficiency. Adding Memcached would improve read performance by caching, but it doesn't address availability or connection efficiency for Bigtable itself, and introduces another component to manage. Increasing the client connection pool size might offer marginal improvements in connection efficiency under heavy load, but it doesn't provide automatic failover or significantly boost availability. Using a Dataflow template with a Beam connector is for data processing and streaming changes, not for improving Bigtable's availability or connection efficiency for an application.