After 18 years of building backends that have survived everything from script kiddies to sophisticated attacks, I've learnt that security isn't just about ticking boxes—it's about understanding why each layer matters. Every scar in production has taught me something, and today I'm sharing the non-negotiable security requirements that form the backbone of any production-ready backend.

Let me be blunt: if you're not setting security headers, you're basically leaving your front door wide open with a "please rob me" sign. These headers are painfully easy to forget, and even easier to misconfigure. I've seen senior devs ship code without them because "we'll add them later." Spoiler: later never comes.

The essential headers you need are like a Swiss Army knife for web security. Content-Security-Policy is your guardian against XSS attacks—it tells the browser exactly what sources it should trust. I once saw a junior dev's innocent console.log() turn into a full-blown XSS vulnerability because we hadn't set this properly. X-Content-Type-Options stops browsers from being clever and guessing MIME types wrong (trust me, browser "helpfulness" is often anything but).

Strict-Transport-Security ensures you're always on HTTPS—no exceptions. X-Frame-Options prevents your site from being framed by dodgy actors (clickjacking is still a thing in 2025, sadly). Referrer-Policy controls what information gets leaked when users navigate away, and Permissions-Policy lets you explicitly control which browser APIs can be used. Configure these once, configure them right, and sleep better at night.

If you're still serving anything over HTTP in production, we need to have a serious chat. HTTPS isn't optional anymore—it's table stakes. But here's the thing: just slapping an SSL certificate on your server isn't enough. You need to enforce HTTPS everywhere, redirect all HTTP traffic (don't just block it—users are lazy and will type http://), and use a strong TLS configuration.

I've seen too many "HTTPS-enabled" sites that still accept TLS 1.0 or weak ciphers. Use TLS 1.2 minimum, preferably 1.3, and keep your cipher suites modern. Let's Encrypt has made certificates free, so there's literally no excuse anymore.

CORS is probably the most cursed and misunderstood part of web security. I've watched developers rage-quit over CORS errors, then "fix" it by allowing everything from everywhere. That's like removing your front door because you're tired of using keys.

CORS exists to prevent unauthorised cross-origin requests to your APIs. Configure it properly: specify allowed origins explicitly, don't use wildcards in production unless you really mean it, and understand that CORS is enforced by browsers, not your server. Your server just sends the rules; browsers enforce them. Mobile apps and backend services ignore CORS entirely, so don't rely on it as your only security measure.

Sessions and CSRF protection go together like Vegemite and toast—you really shouldn't have one without the other. CSRF attacks are sneaky; they trick authenticated users into performing actions they didn't intend. I've seen entire admin panels compromised because someone forgot CSRF tokens.

Use secure, httpOnly, sameSite cookies for session management. Implement CSRF tokens for state-changing operations. And please, for the love of all that's holy, don't store sessions in localStorage if you're dealing with sensitive data—XSS attacks will thank you for the easy access.

JWTs are great for stateless APIs, but they're not magic bullets. I've audited systems where developers thought signing a JWT was enough—no expiry, no refresh strategy, no revocation mechanism. That's like giving someone a lifetime pass to your house and hoping they don't lose it.

Validate tokens on every request (yes, every single one). Implement proper role-based access control—not just "logged in" or "not logged in." Use short-lived access tokens with refresh tokens. And remember: authentication is "who are you?" while authorisation is "what can you do?"—get the distinction clear in your head and your code.

After nearly two decades in this game, if there's one mantra I live by, it's this: never, ever trust user input. Not even a little bit. That innocent-looking form field? It's a potential SQL injection. That file upload? Could be a zip bomb. That JSON payload? Might be trying to overflow your parser.

Validate everything at the edge—check types, formats, lengths, and ranges. But validation isn't enough; you need sanitisation too. Strip out anything that shouldn't be there. Use parameterised queries for databases. Escape output based on context. And remember, client-side validation is just for UX—real validation happens on the server.

Rate limiting isn't just about preventing DDoS attacks (though it helps with that). It's about protecting your backend from that one developer who accidentally put an API call in a render loop (we've all been there). It prevents brute force attacks on login endpoints and stops scrapers from hammering your resources.

Implement rate limiting per IP, per user, and per endpoint. Use sliding windows or token buckets—whatever fits your use case. And please, return proper 429 status codes with Retry-After headers. Your API consumers will thank you.

The best security incident is the one you detect and stop before it becomes a breach. Comprehensive logging and monitoring aren't optional extras—they're your early warning system. Log authentication attempts, authorisation failures, input validation errors, and rate limit violations. But don't log sensitive data—I've seen too many credit card numbers in log files.

Set up alerts for anomalies. Use structured logging so you can actually query your logs. And for crying out loud, actually look at your logs occasionally. That fancy dashboard isn't just for show during investor demos.

Here's the truth: implementing all of this properly is a pain. It's tempting to skip bits, to implement "just enough" security, or to leave it for "phase 2." But I've seen what happens when security is an afterthought—it's not pretty, and it's always more expensive to fix after a breach than to build right from the start.

These eight requirements aren't suggestions or nice-to-haves. They're the minimum viable security for any backend that's going to face the real world. Skip any of them, and you're not just risking your data—you're risking your users' trust, your company's reputation, and probably your job.

So do yourself a favour: bookmark this list, print it out, tattoo it on your arm—whatever it takes to remember it. Because in backend development, paranoia isn't a personality flaw; it's a job requirement.

Stay secure, and may your error logs be forever empty.