The engineering questions you get asked, and the bugs you actually hit. Drawn, one mechanism at a time, in the order the videos ship.
Rate limiters protect servers from traffic surges, DoS attacks, and abusive scraping. How token bucket and leaky bucket work, and which one your API needs.
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.
You asked for a name and a price and thirty-eight fields came back. Every difference between the two is one trade seen from a different side — and the caching bill is where it comes due.
Every request came back 200 and nobody could buy anything. The last two digits have no categorisation role at all — and an error inside a success is a lie three separate systems believe.
REST is six constraints in one chapter of one dissertation, not a synonym for JSON over HTTP — and the spec's own example of getting it wrong is a link a crawler follows to delete your rows.
Three messages before a byte moves, an ACK that isn't a receipt, and the half a ninety-second video has to cut: how fast to send, how much to hold, and where QUIC takes the whole job away.
Four servers, three of which have never heard of the name you asked for, and a cache so you never do it twice — the referral chain in real dig output, plus the CNAME rule that breaks your apex.
Five negotiations run between Enter and the first pixel, and the one nearly every answer skips is that an address and a connection are different things.
Three parties, one redirect, and a code traded for a token. The whole protocol is visible in your address bar, and nobody ever tells you to look.
Not the definition. The four things you actually send, what each one is for, and how to find the one that's wrong.
