I built a free AWS DEA-C01 practice app because I couldn’t find a study tool that fit my routine

I built a free AWS DEA-C01 practice app because I couldn’t find a study tool that fit my routine. Most prep tools sat at two extremes: long video courses that required hours of attention, or static question banks that graded me without teaching me. I wanted something small, fast, and honest about how AWS certification prep actually happens in short sessions between real work.

The app is deliberately boring: scenario-based questions, instant answer rationale, and a review queue for missed questions. No login wall, no streak mechanics, no email drip.

Why DEA-C01 prep feels harder than it should

The AWS Certified Data Engineer - Associate exam covers a wide service surface. You are expected to make decisions across data ingestion, transformation, storage, security, operations, and schema design. The [official AWS exam guide](https://d1.awsstatic.com/training-and-certification/docs-data-engineer-associate/AWS-Certified-Data-Engineer-Associate_Exam_Guide.pdf) is a good map, but most question banks don’t follow that map. They either drill individual services in isolation or throw random questions with no explanations.

That gap is where I got stuck. I could read about [AWS Glue](https://aws.amazon.com/glue/), [Amazon Redshift](https://aws.amazon.com/redshift/), [Amazon Kinesis](https://aws.amazon.com/kinesis/), and [Amazon Athena](https://aws.amazon.com/athena/), but I couldn’t practice service-selection judgment. The real exam rarely asks ‘what is this service?’ It asks ‘which combination meets these requirements with the least operational overhead?’

What the app does

The core loop is simple: answer, explain, review.

Scenario-based questions

Each question is written like a short DEA-C01 scenario. For example: ‘A retail company needs to ingest clickstream events streaming from multiple locations and make them available for ad hoc SQL analysis within a few minutes. Which service combination meets the requirements?’ That style forces you to reason about ingestion, storage, and query access together.

Answer rationale, not just correctness

Every answer includes a short explanation of why the correct answer works and why the distractors fail. Where relevant, the explanation links to official AWS documentation so you can go deeper. This is the part I missed most in other tools.

Missed questions become a review queue

You don’t need to create a study plan manually. Missed questions go into a local review queue. Revisit them until the pattern sticks.

Practice mode and timed mode

Practice mode gives immediate feedback. Timed mode simulates an exam block and shows a raw score at the end. No false precision, just a way to build pacing.

No account, no backend

Progress is stored in your browser. The goal is to make opening the app as close to frictionless as possible.

Technical choices

I built the app as a static Next.js site on Vercel. Question content lives in Markdown files in Git, not a database. That keeps review simple and makes community contributions easier. Because there is no server session and no user data collection, the app stays free and cheap to operate.

The UI uses a warm canvas and restrained typography. That’s intentional: long question sessions feel less exhausting when the interface stays quiet.

What I’m looking for

I’m looking for specific feedback from people actively preparing for DEA-C01 or anyone who has recently passed.

Are the explanations too deep, too shallow, or about right?

Do the scenario questions feel close to the real exam?

Should timed mode include per-domain scoring?

Would you contribute questions if the template were a simple Markdown file?

I want to keep the app free and focused. If a feature improves study effectiveness, I’ll add it. If it adds noise, I won’t.

I’m opening the comments for feedback from anyone currently prepping for DEA-C01 or who has already passed.