Req, Res, Flow
This HTTP method is most commonly used when submitting form data to create a new record.
What is POST?
This hook stores values that cause a component to re-render when updated.
What is useState?
This CRUD operation retrieves existing data from the database.
What is Read?
If this is missing from a POST request, your server may reject the request or store bad data.
What is required request data or a request body?
This JavaScript keyword allows reassignment and is block-scoped.
What is let?
After Express finishes processing a request, it sends this back to the client.
What is an HTTP response?
This hook is used for side effects like data fetching or subscriptions.
What is useEffect?
This Mongoose feature defines the shape and validation rules of stored data.
What is a schema?
If this middleware is not enabled, Express won’t understand incoming JSON.
What is express.json()?
This array method is commonly used to transform API response data for display.
What is map()?
This is the typical data path when React successfully retrieves data from an API.
What is React → Express → Database → Express → React?
This React pattern ensures form inputs are always in sync with component state.
This React pattern ensures form inputs are always in sync with component state.
This database action modifies existing data without creating a new document.
What is Update?
If users can access protected routes without logging in, this layer is missing or misconfigured.
What is authentication or authorization middleware?
This array method is often used to remove unwanted items from API data.
What is filter()?
This Express feature ensures incoming request data is readable in JavaScript.
What is JSON parsing middleware (express.json).
This mistake can cause an infinite loop when fetching data.
This mistake can cause an infinite loop when fetching data.
This is a key reason MongoDB works well in JavaScript-heavy stacks like MERN.
What is storing data as JSON-like documents.
If your frontend never updates after a successful API call, this React step is likely missing.
What is updating state with the server response?
You use this pattern to safely handle async code that might fail.
What is a try/catch block?
An interviewer asks what happens if the server returns an error instead of data.
What is handling the error response and updating UI state?
An interviewer asks why state changes trigger UI updates automatically.
What is React’s re-rendering based on state changes?
An interviewer asks why you wouldn’t put business logic directly in your routes.
What is separation of concerns?
An interviewer asks how you prevent the UI from breaking when the server sends back an error.
What is handling errors in React state and displaying feedback?
An interviewer asks why async code is necessary in a MERN app.
What is allowing the app to keep running while waiting for API or database responses?