AWS Redis Connectivity Issue Analysis (Required DevOps Engineer )

I have a Node.js backend running in Elastic Beanstalk (EC2 instances) that relies on ElastiCache Redis for chat and socket traffic. Both services live inside the same VPC, the Redis endpoint listens on 6379, and my Redis security group is already open to the backend security group. Outbound rules on the backend are wide-open.

Despite this, the application log is flooded with:

Redis error: connect ETIMEDOUT

So far I have:
• double-checked every security-group rule, and
• confirmed that each component sits in the correct VPC and subnets.

I need an experienced AWS/DevOps engineer to dig deeper, explain the most probable causes of ETIMEDOUT in this scenario, point out (and ideally correct) any missing network layers—NACLs, route-table entries, subnet selection, DNS settings, IAM policies, or anything else that can block or throttle the connection—and show me how to test connectivity properly from the EC2 instances to the Redis cluster (telnet/nc, redis-cli, VPC Reachability Analyzer, etc.).

Deliverables
• Clear diagnosis of the root cause
• Step-by-step remediation or configuration changes (with CLI or console screenshots/commands)
• A short validation checklist so I can confirm the fix in the future

If you’ve untangled similar AWS networking puzzles before, let’s get this solved quickly.