Backend dev feeling shaky on networking fundamentals — is this the right roadmap / order?

My day-to-day job is writing FastAPI endpoints — I build the route plus the backend logic behind it. No database work, no auth, nothing lower-level than that. It's been fine for the job itself, but I've realized I don't actually understand what's happening below my own function calls, and it's bugging me. If someone asked me to debug a networking-related issue (a timeout, a 502, a service that can't reach another service) I honestly wouldn't know where to start.

I asked Claude to help me put together a roadmap specifically for networking as a backend/DevOps engineer — not full network-engineer depth (no subnetting math, no BGP, no Cisco config), just enough to actually understand and debug what's happening around the code I write. Here's what it gave me:

1. HTTP — requests/responses, methods, status codes, headers
2. DNS — how a domain becomes an IP, from the client side
3. TCP vs UDP — how data actually gets transported
4. TLS/HTTPS — what "encrypted in transit" means in practice
5. Sockets & ports — what "a server is listening" means at the OS level
6. Reverse proxies & load balancers — why an app almost never talks directly to the internet
7. API Gateways — managing access/routing across multiple services
8. Containers & service discovery — how containers find and talk to each other
9. Cloud reachability — public vs private, firewall-type rules
10. Debugging tools — curl, dig, ss/netstat, tcpdump

Questions for anyone who's actually been through this:

• Is this the right order to learn these in, or would you sequence it differently?
• Am I missing anything that turned out to matter a lot in practice once you were past the "junior" stage?
• For those doing backend/DevOps day to day — which of these do you actually reach for regularly vs. which ended up being more "nice to know"?

Appreciate any input — trying to close this gap properly instead of just picking things up piecemeal when something breaks.