Part 5: Monitoring & Alerting Gaps That Let ECS Failures Slip Through

This is Part 5 of 5 in my series on keeping ECS deployments rock-solid — covering best practices, hidden pitfalls, and the sneaky issues that cause downtime.

Sometimes the worst ECS failures aren’t the ones that crash loudly — they’re the ones that fail quietly.
I’ve seen services run “successfully” in ECS while the app inside was broken for hours because no alerts fired and no one was watching the right metrics.

If you’re relying on someone to notice and tell you something’s wrong, you’re playing production roulette.

Here are 3 monitoring & alerting mistakes I’ve seen teams make — and how to avoid them.

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1️⃣ No Task-Level Metrics

The Problem:
ECS gives you service-level health, but that doesn’t always tell the full story.
A single task might be spiking CPU, running out of memory, or constantly restarting without ever failing the service as a whole.

Fix:

• Enable CloudWatch Container Insights for ECS.

• Set alarms on per-task CPU and memory usage to catch runaway containers early.

• Monitor task restarts — high restart counts usually mean something’s wrong in the app.

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2️⃣ Ignoring ALB Metrics

The Problem:
The ALB knows more about your app’s availability than ECS does — but many teams ignore its metrics.
I’ve caught outages faster by watching ALB’s UnHealthyHostCount than by looking at ECS dashboards.

Fix:

• Create CloudWatch alarms for UnHealthyHostCount and TargetResponseTime.

• Pair them with notifications via SNS to Slack, email, or PagerDuty.

• Don’t just set alerts — test them by intentionally failing a container.

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3️⃣ No End-to-End Synthetic Checks

The Problem:
Even if ECS tasks and the ALB are “healthy,” your actual user journey might still be broken — login failing, payment API timing out, etc.
Without synthetic checks, you won’t catch these.

Fix:

• Use a tool like Gatus, Pingdom, or CloudWatch Synthetics to run regular HTTP checks against critical endpoints.

• Include flows that mimic real user actions, not just a /health check.

• Alert if these fail more than once in a short period.

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💡 Bonus Tip:
Monitoring is only half the job — alert routing matters just as much.
If an alert triggers at 3 a.m. and goes to the wrong inbox, it might as well not exist.

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Final Thought

Good ECS deployments don’t just run well — they tell you when something’s wrong, ideally before users even notice.
Watch the right metrics, test your alerts, and make monitoring part of your deployment checklist.

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Now that we’ve covered:
1️⃣ Health checks
2️⃣ Container & image issues
3️⃣ ALB misconfigurations
4️⃣ Networking pitfalls
5️⃣ Monitoring gaps

…you’ve got a solid checklist for avoiding the most common ECS downtime traps.