If you’re running an startup, your cloud bill is probably your second or third largest expense — right behind salaries. And if you’re like most of the founders we talk to, you’re overpaying by at least 30%.

That’s not because you’re doing anything wrong. It’s because cloud pricing is designed to be confusing and when you’re moving fast, optimizing infrastructure is the last thing on your mind.

Here are the five most common mistakes we see — and what to do about them.

1. Running Everything On-Demand

This is the biggest one. Most startups spin up instances and just… leave them on the default on-demand pricing. Cloud providers love this because on-demand is their most expensive option.

The fix: For any workload that runs consistently, you should be using reserved instances or savings plans. For AI training jobs that can tolerate interruptions, spot instances can cut costs by 60–90%.

We helped a seed-stage AI company switch their training workloads to spot instances with automatic checkpointing. Their GPU bill dropped from $8,400/month to $2,800/month — overnight.

2. Oversized Instances “Just in Case”

It’s tempting to provision big machines so you don’t have to worry about capacity. But “just in case” is expensive when you’re paying for CPU, memory and GPU resources 24/7.

The fix: Right-size your instances based on actual usage data, not guesses. Most cloud providers have built-in tools to show you utilization metrics. If your average CPU usage is 15%, you’re paying for 6x more than you need.

3. Paying for Idle Resources

Development environments running on weekends. Staging clusters that nobody’s used in weeks. Data pipelines processing test data on production-grade hardware.

The fix: Implement automated schedules. Dev environments should shut down outside business hours. Use serverless or scale-to-zero for non-critical workloads. This alone typically saves 15–25%.

4. Ignoring Data Transfer Costs

This one sneaks up on you. Cloud providers charge for data moving between regions, between services and out to the internet.

The fix: Keep data processing in the same region as your storage. Use CDNs for serving static assets and model artifacts. Compress data before transfer. And review your architecture for unnecessary cross-region traffic.

5. No Visibility Into Spending

You can’t optimize what you can’t see. If you’re just looking at one big number on your cloud bill each month, you’re flying blind.

The fix: Set up cost allocation tags on every resource. Break down spending by team, project and environment. Set up alerts for anomalies. Most importantly, review costs weekly - not monthly.

The Bottom Line

Cloud cost optimization isn’t about being cheap. It’s about being smart with your runway. Every dollar you save on infrastructure is a dollar you can spend on building your product, hiring your team or extending your runway.

At Kernul, we’ve helped over 40 startups reduce their cloud bills by an average of 37%. If your cloud bill is growing faster than your revenue - let’s talk.