Choose the Store's Database Without a Fight
Work from the brief alone. Write what you would produce — actors, requirements, data, a first slice, your unknowns — before opening anything below it; the exercise stops working if you read the reality first.
Two engineers are certain: one says PostgreSQL, one says MongoDB for the store's primary database. The decision is needed this week. Produce a trade-off matrix without fake precision, classify the decision's reversibility, state what would have to be true for each option to win, and write the decision record.
Your attempt
Nothing here is checked. It exists so that the reveal below is a comparison rather than a reading.
Running a week of benchmarks to settle it "objectively". The benchmark needs a workload, and choosing the workload is the decision the matrix would have made in an hour; the week produces numbers each side reads as confirmation, and the decision is made by whoever is more tired.
Read this even if you are confident. It is here rather than behind a button because it is the move most people actually make, it produces things that look like a project, and its cost arrives when the first hard requirement has nowhere to go.