Hello Reader,

As a former Principal Solutions Architect at AWS, and Distinguished Cloud Architect at Verizon, I conducted 300+ interviews.

And every cloud interview has this question.
​Every. Single. One.

"How will you make your application scalable for a big traffic day?"

And almost every candidate gives the same answer: "I'll use an Auto Scaling Group with EC2s and a load balancer to distribute traffic."

Technically correct. Completely average. Three years ago that answer was fine.

Today it will not get you hired.

Here is the answer that will - start with the foundation - then go deeper.

Yes, you use an Auto Scaling Group and a load balancer. That is table stakes. But a big traffic day like Thanksgiving or Diwali means a massive burst of traffic in a very short window. The standard autoscaling response is too slow for that.

So here is what you add:

Pre-warm the load balancer. Elastic Load Balancer scales automatically, but if the traffic spike is sudden and enormous, there can be a brief lag. You can pre-warm it by submitting a support request directly from the AWS console before the event.

Use Scheduled Scaling with Warm Pool. If you know traffic is hitting at 8pm on Black Friday, why wait for the CPU threshold to trigger scaling?

Schedule your EC2s to provision ahead of time. Pair that with a Warm Pool - a set of pre-initialized EC2 instances sitting ready in your Auto Scaling Group. When traffic arrives, those instances spin up faster because the initialization work is already done.

Keep your AMI lightweight. Every unnecessary package on your AMI adds provisioning time. Trim it down so new EC2s come online as fast as possible.

Add RDS Proxy for database connections. This one trips up a lot of candidates because they forget the database layer entirely.

When your application scales out to hundreds of EC2s, each one tries to open a connection to your database. Without a proxy, you get orphaned connections, connection pool exhaustion, and latency spikes - exactly when you can least afford it.

RDS Proxy manages the connection pool, reduces the number of new connections being initialized, and keeps your database stable under load.

Add Caching. Add caching layer to reduce unnecessary load on compute and database. Keep in mind, that caching is for read requests only, and not write.

Implement CloudFront in front of ALB, and/or a caching database between application code running in EC2 and the Database.

Run AWS Countdown. This is the answer that only comes from real-world enterprise experience. AWS Countdown is an activity you run with your AWS account team before a high traffic event.

AWS simulates the load with all your parameters in place. If something is off, maybe the load balancer needs more pre-warming, or the scheduled scaling numbers need adjusting - you catch it before the big day, not during it.

Check your account limits. There are soft limits and hard limits on your AWS account. For a massive event, you may need to request a soft limit increase in advance.

For truly enormous traffic (think a new iPhone launch), you might even need to distribute across multiple accounts and regions.

One mistake I see constantly

As soon as the interviewer says "high traffic day," candidates immediately pivot to Kubernetes or serverless as if that solves everything.

It does NOT.

Whether you are on EC2, Kubernetes, or Lambda - these high-scale challenges still exist. You still need to think about scheduled scaling, warm pools, database connection management, and account limits.

Moving to containers does not eliminate the problem. It just changes which layer you solve it at.

Knowing that distinction is what separates a candidate who has read about cloud from one who has actually shipped production systems.

The delight answer in one sentence:

The average candidate talks about Auto Scaling Group and load balancer. The hired candidate talks about pre-warming, warm pools, scheduled scaling, lightweight AMIs, Caching, RDS Proxy, AWS Countdown, and account limits - in a structured answer that shows they have done this for real.

That is the answer that makes an interviewer put down their pen and say "okay, this person has been in the trenches."

Question for you: Have you ever had to prepare an application for a big traffic event in production? What did you wish you had known beforehand? Hit reply, I read every response.

Keep learning and keep rocking 🚀,

Raj

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