Why we should have data validation checks in every backend application?

How do we know if the data sent by client is what we asked for.

For example:

Assuming MERN tech stack

We need pageSize and pageNumber as query parameters in a URL. By default these parameters should be number but what if client/Frontend does not send number? It could crash our server.

Reasons we should have data validation checks:

• Prevent malicious database commands to reach our database
• Give client exact error why request is failing
• Reduce response time
• Does not crash server

Where to put validation check?

We should place validation check right after we receive request. I will tell you in order

1. Validation check

2. Business logic

3. Database call

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