How do you protect a web application from someone sending malicious input, such as an SQL injection attack?

What the interviewer is looking for

• This question tests security fundamentals. Mentions input validation, parameterised queries, authentication and authorisation, secret management and least privilege without prompting.
• Strong answers: Parameterised queries or a safe query builder, validating and sanitising input, escaping output, least-privilege database accounts, and not trusting the client.
• Likely follow-up: What other common attacks do you keep in mind when building an endpoint?

Another way it may be asked: Someone types strange code into your search box hoping to read your database. How does your backend stop that?

A structure to follow: Answer, explain, example, limits

1. Step 1

   Answer

   Give your direct answer in the first sentence so the interviewer knows where you are going.

2. Step 2

   Explain

   Say how it works or why you would do it that way, in plain words before jargon.

3. Step 3

   Example

   Anchor it in something you have actually done or seen, with the detail that shows hands-on experience.

4. Step 4

   Limits

   Say when your approach would not be the right one. It shows judgement.

This is guidance on shape, not a script. Use your own real experience and facts; never invent details to fill a gap. See the STAR guide and answer frameworks.

Common slips

• Reciting a definition without showing you have applied it.
• Using terms you cannot explain if asked a level deeper.
• Claiming experience beyond what you can discuss in detail.

How to practise it

Say the answer in 90 seconds, then answer the follow-up as if it were a new question.

Related questions

• How do you handle secrets like database passwords and access keys in your services?
• If you were building an API for a simple to-do app, what endpoints would you create, and how would you handle errors?
• What is a database index, and how would you decide whether a column needs one?
• Tell me about a time you changed a database schema on a live system. How did you do it without downtime?
• An endpoint starts timing out in production at peak hours. How would you investigate, and what would you look at first?

Browse all questions