The engineering questions you get asked, and the bugs you actually hit. Drawn, one mechanism at a time, in the order the videos ship.
How algorithm negotiation and ciphersuite confusion create critical security vulnerabilities in JWTs, and how PASETO v4 enforces modern cryptographic safety by default.
How PostgreSQL process concurrency causes connection exhaustion, and how PgBouncer transaction pooling enables 10,000+ serverless functions to share 50 database sockets.
A deep dive comparing full-duplex WebSockets, unidirectional Server-Sent Events (SSE), and asynchronous Webhook callbacks for modern web systems.
401 means 'I don't know who you are (authenticate yourself)'. 403 means 'I know who you are, and you don't have permission'. The naming mistake in HTTP and how to use them.
XSS executes malicious code inside your user's browser. CSRF tricks your user's browser into making requests they never wanted. The key difference in one line.
String concatenation turns user input into executable database commands. Why escaping strings fails and parameterized queries always win.
Encryption is a two-way street with a key. Hashing is a one-way mathematical trapdoor. Why speed is the enemy of secure passwords.
Your server returned 200 OK, Postman works fine, and your frontend console is red. CORS is not a server error; it is a browser security sandbox.
You changed the price an hour ago and somebody just paid the old one. HTTP gives a server exactly one way to remove something from a cache, and it is a side effect rather than a command.
The page said welcome back, with somebody else's name on it. Four questions decide whether something in the path may answer instead of your server — and the default, when you say nothing at all, is not 'don't cache'.
