marketing departments of cloud providers have been telling us the same tale for years: “Forget the infrastructure, focus only on your code, only pay for what you use.” Sounds great, doesn't it? In theory, yes. But in practice, Serverless can sometimes become an invisible financial black hole
.Let's be honest; the “pay-as-you-go” model evolves very quickly into the “Pay-as-you-panic” model if you don't know exactly what you're doing. Let's look with a skeptical eye at the hidden costs behind those brilliant presentations and how to survive this chaos
.1. There's No Such Thing as “Free”: Invisible Killers
When it comes to Serverless, all people think of is Execution Time. You account for “My function worked 100ms, I paid that many pennies”. You are wrong. The main items that inflate the bill are usually:
- Data Transfer (Egress): Exiting data out of the Cloud is often expensive from the function itself.
- API Gateway: That “gateway” where you open Lambda or Azure Functions doors to the world, sometimes generates more costs than the processing power behind it.
- Logging & Observability: The moment you said, “Let's log everything, we need to”, you burned out. Log Ingestion fees for CloudWatch or similar services can make you say “I wish I didn't know so much” at the end of the month .
2. Cold Start: Not Just Performance, It's a Waste of Money
Everyone talks about Cold Start's latency problem. But a skeptical expert asks: “How much money do I lose during this delay?” If your application is user-facing and leaves the user cart because of that 2-second delay, the cost of that function is much more than $0.00001 in the technical documentation.
Scaling is fine, but the line between the cost of an idle Provisioned Concurrency and the cost of a traditional VM is thinner than you think.
Architectural Decision 3: When to Escape?
At some point you have to stop and ask: “Why don't we use Kubernetes or a bare-metal server?” If your traffic is stable, predictable, and high 24/7, Serverless is the most expensive
choice for you.Serverless is a godsend for spiky (uncertain and skyrocketing) traffic. But using Serverless on a constantly running system is akin to taking a taxi to work every day. It makes much more sense to buy (or rent) a car after a certain point
.4. The “Real” Recipe for Optimization
So, how do we protect the wallet?
- FinOps Culture: Cost tracking is not only the job of the accountant, but also of the developer. You can't be a “Senior” without knowing how much the code you write costs . The
- Granularity Trap: Breaking the application into thousands of small functions (Nano-services) increases the cost of management and communication. Make logical groupings.
- Timeout Settings: 5 minute timeouts left by default are dangerous. You don't want to pay the bill for the function that enters an erroneous loop.