P2: ElastiCache miniredis instance leak and missing failover features #683

Summary

Resource Leaks

• Miniredis instance not closed on all error paths: If CreateClusterWithOptions fails after miniredis started (e.g., parameter group check), Redis instance leaks ports and memory.

Bugs

• Resource cleanup race in CreateClusterWithOptions: Nested lock acquired after initial operation.
• Potential nil pointer in ListTagsForResource: Multiple clone() calls on potentially nil Tags.

Missing Features

• No automatic failover / primary-replica promotion
• No multi-AZ support
• No cluster scaling (horizontal or vertical)
• No online resharding
• No event notifications
• No parameter group validation against family
• No engine version upgrades
• No maintenance window support

Files

• services/elasticache/backend.go