SQL, System Design and Aptitude: A Student Study Plan

Prepare with small datasets, clear design exercises and a four-week reasoning routine.

By NextPeer Editorial · 2 min read

Prepare for the role you want

Interview preparation should follow the role's requirements. SQL, system design and aptitude are different skills. Use job descriptions and confirmed assessment instructions to decide which topics deserve the most time.

SQL: answer questions with data

Start with SELECT, WHERE, ORDER BY and GROUP BY. Practise joins using a small dataset with customers, orders and products. Explain how null values and duplicate rows affect your result.

Exercises: calculate sales by month, identify customers without orders and find the highest-selling products. Check your answers against a hand-calculated example before increasing the dataset size.

System design: explain the flow

Start with a small system such as a college registration portal. Identify users, requirements, data entities and API operations. Explain how requests reach the application and how data is stored.

Discuss authentication, permissions, validation, failure handling and backups before introducing advanced infrastructure. Separate measured requirements from assumptions about traffic.

Aptitude: practise reasoning

Review percentages, ratios, averages, time and work, and basic probability. Write each step and check units. For logical reasoning, state the information provided and avoid introducing unstated assumptions.

Use timed practice after you understand the method. Review errors by type: misunderstood question, calculation mistake or missing concept.

A four-week practice plan

1. Week one: SQL filtering and aggregation, percentages and ratios, and request-response fundamentals.
2. Week two: SQL joins, averages and work-rate problems, and a small database design.
3. Week three: mixed SQL exercises, timed reasoning sets, and API and permission design.
4. Week four: mock tasks, error review and explaining solutions aloud.

Measure readiness

You should be able to explain a query's result, justify a design choice and show the steps in a reasoning problem. These observable skills help you identify the next gap more accurately than a single practice score.