Panel-ready MERN Full Stack questions for freshers and experienced developers. Practice at Coding Cadre in Faridabad, or Online from Delhi NCR.
The user requests a reset
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A Dockerfile packages Node, dependencies, and start command so the app runs the same on every machine.
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Platforms such as Render, Railway, or AWS inject env vars into the process at runtime.
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A reverse proxy such as nginx receives public traffic and forwards it to Express.
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A process manager can start a new worker, wait until it listens, then stop the old one.
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Atlas rejects connections from IPs that are not on the allowlist.
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Query the UI the way a user would, by role, label, and text, not by component internals.
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Replace the network layer with a stub that returns canned JSON so tests stay fast and offline.
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Supertest issues HTTP requests against your Express app without opening a real port.
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A stub returns prepared data so the unit under test can run.
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Coverage only shows which lines ran, not whether assertions would catch a bug.
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Cross-site request forgery tricks the browser into sending a victim's cookies to your API from another site.
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If you pass untrusted JSON into a query, an attacker can send operators such as $gt and change the filter.
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Use HTTPS-only cookies, HSTS, a Content-Security-Policy for the React app, X-Content-Type-Options, and a tight Referrer-Policy.
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Rate-limit by IP and account, add backoff, and consider CAPTCHA after failures.
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Mass assignment happens when the API saves every field the client sent, including role or isAdmin.
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Socket.IO adds rooms, automatic reconnection, and fallbacks such as long polling.
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Namespaces split the socket server into logical apps, such as /chat versus /notifications.
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Send the access token in the handshake auth payload or a cookie and verify it before joining rooms.
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Some proxies, firewalls, or old browsers block the WebSocket upgrade.
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