AWS ElastiCache Support
Fix ElastiCache cannot connect and timeout errors.
ElastiCache lives inside a VPC and has no public endpoint, so most connection failures are network, TLS or authentication mismatches. A timeout and a refused connection mean different things. We test each layer from the client and fix the one that fails.
When You Need This
The situations where this work pays for itself.
Signs it is time
- A client times out connecting from EC2, ECS or Lambda
- Connections work from one subnet but not another
- You enabled encryption in transit and clients now fail
- A cluster mode client reports MOVED or cannot find slots
- You try to connect from your laptop and nothing happens
What you get
- Root cause of the failure with the failing layer identified
- Corrected security group, subnet and routing configuration
- Client configuration for TLS, AUTH and cluster mode
- A secure developer access method
How we do it
A clear, safe process you can follow along with.
1. Use the right endpoint
We confirm the endpoint: the primary or configuration endpoint for cluster mode, the reader endpoint for reads, and not an individual node address that changes after failover.
2. Check the network path
The client must be in the same VPC, or connected by peering, Transit Gateway or VPN. A timeout usually means a security group, network ACL or routing problem, and not an application issue.
3. Check security groups
The cache's security group must allow inbound on the Redis port (6379 by default) from the client's security group or CIDR. We verify with nc or redis-cli from the client host.
4. Check TLS and AUTH
With in-transit encryption, the client must use TLS, for example redis-cli --tls or rediss://. Mismatches cause resets or protocol errors. If AUTH or access control lists are enabled, the client must supply the right token or user.
5. Check Lambda and container specifics
Lambda must be attached to the VPC with subnets and security groups that reach the cache. Containers need the right task security group and subnet routing.
6. Check client library behavior
Cluster mode needs a cluster-aware client that follows MOVED redirects. We also check connection timeouts, pool settings and DNS resolution of the endpoint.
7. Reach it from outside when needed
For developer access, we use a bastion host, SSM port forwarding or VPN, not a public endpoint.
Mistakes we help you avoid
Common ways this goes wrong, and what we do instead.
Opening the security group to 0.0.0.0/0
ElastiCache should accept traffic only from your application tier.
Using plain redis:// with encryption in transit
Use TLS, or connections are reset.
Pointing at a node endpoint
Node addresses change after failover. Use the primary or configuration endpoint.
Frequently Asked Questions
Why can't I connect to ElastiCache from my laptop?
ElastiCache does not expose a public endpoint. Connect through a bastion host, SSM port forwarding, VPN or Direct Connect into the VPC.
Why does my connection time out?
A timeout almost always means traffic is blocked or not routed: a security group, network ACL, wrong subnet or a client in another VPC without connectivity.
Why do I get MOVED errors with Redis?
The cache runs in cluster mode and your client is not cluster-aware. Use a cluster client and the configuration endpoint.
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