Difficulty: Medium
Description
We identified several ElastiCache clusters in your account running on older instance families (t2, t3, r4, r5, m4, m5). AWS Graviton-based instances of the next generation offer equivalent or better performance at a lower cost — typically 15-25% savings with no application changes required.
Selection Criteria
The ElastiCache instance family is one of:
cache.t2,cache.t3,cache.r4,cache.r5,cache.m4,cache.m5.A Graviton equivalent instance is available in the same region.
Expected Saving
Migrating to Graviton instances typically yields 15-25% savings on compute costs with equivalent or better performance.
Current Family | Graviton Target | Estimated Savings |
cache.t2. / cache.t3. | cache.t4g.* | ~20% |
cache.r4. / cache.r5. | cache.r6g.* | ~20% |
cache.m4. / cache.m5. | cache.m6g.* | ~20% |
Example: cache.r5.large (~$0.238/h) → cache.r6g.large (~$0.191/h) = ~$34/month savings
⚠️ Reserved Instances : changing instance family may not be covered by an existing RI. Verify RI scope before migrating.
Operational Impact
Redis with replication group (Multi-AZ) : automatic failover — brief interruption (~60 seconds).
Single-node Redis : brief downtime during the instance modification (a few minutes).
⚠️ Memcached : all cached data is lost during the modification — applications must handle a cold cache after the change.
⚠️ Reserved Instances : verify that an active RI covers the new instance family before proceeding. If not, the RI continues billing on the old family.