Hey folks! We recently faced a huge bill of $9.7k due to a NAT Gateway in the ap-south-1 region racking up an astonishing 4 TB of egress traffic daily for 30 days. It all seemed safe at first—two private subnets and one NAT per availability zone—until our finance team saw the bill. The driving factor was a new micro-service making 5,000 requests per minute to an external API, with all egress routed through the NAT (no prefix lists or endpoints in sight). Unfortunately, our Cost Explorer alerts only went off after the month closed.
In response, we took the following steps to mitigate this:
1. Set up daily Cost Explorer alerts for NAT Gateway traffic.
2. Implemented VPC endpoints for numerous services like S3 and DynamoDB.
3. Adjusted our NAT to an HA t4g.medium instance.
4. Introduced traffic deduplication and compression using Envoy/Squid.
5. Planned quarterly architecture reviews to spot new issues.
Now, I'd love to hear: What AWS features or proactive measures would you recommend to catch such costs in real-time or tactics you've successfully implemented to avoid runaway egress costs? Looking forward to your insights and horror stories!
5 Answers
One of the simplest yet most effective ways to catch these costs is by setting up billing alerts. You can establish budget reports that notify you as you approach your spending limits. These alerts are crucial for any new service or frequently used service to ensure you keep a close eye on your costs.
Having budget alerts set at intervals like 25%, 50%, and 75% of your budget would help you stay on top of sudden spikes.
That level of outbound traffic could easily go unnoticed if not monitored closely. Implementing some form of external traffic monitoring is key, as it would alert you to unusual traffic patterns, which could indicate potential issues like data exfiltration.
Absolutely! It’s scary how unnoticed large traffic spikes can go without proper visibility.
Right? We revamped our monitoring strategy after a similar incident; it’s a must-have now.
We set up a daily Slack post to see yesterday's costs for our top services. This way, changes are spotted quickly, giving us an immediate heads-up on any increases. I'll share a GitHub link if anyone's interested!
That sounds like a fantastic tool! I'd love to see that GitHub repo.
Yeah, I would love to incorporate that into our daily routine. Thanks for sharing!
There are indeed several CloudWatch metrics you can track that would alert you about unusual traffic levels, like monitoring the API requests per minute. This kind of proactive alerting can prevent costly surprises significantly.
Exactly! Setting alarms for these metrics would greatly enhance your visibility into traffic spikes.
Just a reminder: it's important to regularly review metrics that actually affect your costs, like outbound traffic.
You should definitely take advantage of AWS Cost Anomaly Detection. It identifies unusual spending patterns and can notify you quickly based on the thresholds you define. This tool can catch unexpected spikes like this before they become an expensive mistake.
That's true! We integrated Cost Anomaly Detection from the beginning, and it's already saved us from several issues.
I use this feature for both daily and weekly checks, and it really helps prevent surprises in my billing.
I totally agree! I always set up billing alerts, and it's saved me from unexpected bills multiple times.