CloudWatch Metric Guide
CurrConnectionsAmazon ElastiCache CloudWatch metric
CurrConnections reports the number of client connections open to the node at the moment it's sampled. For Redis/Valkey it excludes read-replica connections and a handful (4–6) of connections ElastiCache itself uses to monitor the cluster; for Memcached the reserved/internal count differs slightly.
What it measures
About CurrConnections
CurrConnections reports the number of client connections open to the node at the moment it's sampled. For Redis/Valkey it excludes read-replica connections and a handful (4–6) of connections ElastiCache itself uses to monitor the cluster; for Memcached the reserved/internal count differs slightly.
| Namespace | AWS/ElastiCache |
| Metric name | CurrConnections |
| Unit | Count |
| AWS docs | Official Amazon ElastiCache metrics reference |
Why this metric matters
Connection growth on ElastiCache almost never reflects legitimate traffic growth on its own — Redis/Valkey and Memcached clients are meant to hold a small, stable pool of long-lived connections, not open one per request. When CurrConnections climbs steadily rather than plateauing, it's a strong signal of a connection leak: application code (or a serverless/Lambda caller without a shared pool) opening new connections faster than it closes them.
The failure mode is abrupt rather than gradual. Once CurrConnections reaches the engine's maxclients limit (a configurable parameter, default 65,000 on modern node types but far lower on constrained configurations), every new connection attempt is rejected outright — visible as a spike in the RejectedConnections metric — and the application sees connection errors with no graceful degradation in between.
Recommended alarm threshold for CurrConnections
Recommended threshold
> 80% of the cluster parameter group's maxclients value, sustained for 5 minutes
AWS documentation does not publish a fixed number here either — it states only that "an increasing number of CurrConnections might indicate a problem with your application" and directs you to investigate. The 80%-of-maxclients threshold is a Nuberio recommendation, mirroring the same percentage-of-limit pattern AWS itself uses for RDS's max_connections: it leaves enough headroom to intervene (restart a leaking client, scale out) before the engine starts rejecting new connections outright.
Is your CurrConnections alarm already set up correctly?
The free Nuberio Audit scans your CloudWatch setup and flags missing or misconfigured alarms — including CurrConnections — in 5 minutes.
Common failures that show up in CurrConnections
When CurrConnections reaches an alarm threshold, these are the most common root causes — in order of how often Nuberio sees them across customer AWS accounts.
Application-side connection leak — clients opened per request (or per Lambda invocation) without a shared connection pool, never explicitly closed
No connection pooling configured at the client library level, so each new request or worker process opens its own raw connection
A deploy or autoscaling event briefly doubling active connections as old and new application instances overlap
A misbehaving retry loop reconnecting repeatedly instead of reusing an existing connection after a transient network blip
Fan-out from many short-lived serverless invocations each establishing a fresh connection instead of reusing one across warm starts
How the Nuberio Audit checks CurrConnections
The free Audit scans every Amazon ElastiCache resource in your account and checks whether a CurrConnections alarm exists, whether its threshold and evaluation period are configured sensibly, and flags it if it's missing entirely. Every finding comes with the exact CLI command to fix it — read-only access, no credit card, results in about 5 minutes.
Nuberio Audit
Scans your CloudWatch setup for missing or misconfigured CurrConnections alarms. Free, 5-minute read-only scan.
Related Amazon ElastiCache metrics
CurrConnections rarely fails in isolation. These metrics tend to correlate — monitor them together for complete Amazon ElastiCache coverage.
FAQ
Frequently asked questions about CurrConnections
Common questions about setting up CloudWatch alarms for CurrConnections in Amazon ElastiCache.
What is the recommended CloudWatch alarm threshold for CurrConnections?+
> 80% of the cluster parameter group's maxclients value, sustained for 5 minutes. AWS documentation does not publish a fixed number here either — it states only that "an increasing number of CurrConnections might indicate a problem with your application" and directs you to investigate. The 80%-of-maxclients threshold is a Nuberio recommendation, mirroring the same percentage-of-limit pattern AWS itself uses for RDS's max_connections: it leaves enough headroom to intervene (restart a leaking client, scale out) before the engine starts rejecting new connections outright.
Which CloudWatch namespace does CurrConnections belong to?+
CurrConnections is published in the AWS/ElastiCache namespace with a unit of Count. You can find it in the CloudWatch console under "Metrics" → "AWS/ElastiCache". See the Amazon ElastiCache CloudWatch metrics reference in the AWS documentation.
Does Nuberio automatically create CloudWatch alarms for CurrConnections?+
No — the free Nuberio Audit does not create alarms for you. It scans your CloudWatch setup and tells you which Amazon ElastiCache resources are missing a CurrConnections alarm, then gives you the exact CLI command to create it yourself.
Can I use Nuberio without already having a CurrConnections alarm set up?+
Yes. The free Audit works whether or not you have any CurrConnections alarm configured — it reads the resource directly from CloudWatch and tells you which resources need one, plus the copy-paste AWS CLI command to create it.
This page is part of the CloudWatch metric guide — thresholds and debugging guidance for every metric across RDS, Lambda, ECS, ALB, EC2, and DynamoDB. To find which Amazon ElastiCache alarms your account is missing — including CurrConnections — run the free CloudWatch alarm audit. The scan takes under 5 minutes and requires no account.