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Review cards · 16 cards

Networking

DNS, load balancers, proxies and what happens between the client and the first server.

Train networking in daily review

Cards

  1. You are about to take a server out of the load balancer for a deploy. What should happen first so no user sees an error? easy Multiple choice
  2. On a cache miss, a recursive DNS resolver asks the _____ servers, then the _____ servers (such as .com), and finally the domain's _____ name servers. easy Fill in the blank
  3. You need to send /api/* requests to one pool of servers and /static/* to another. Which load balancer can do this? easy Multiple choice
  4. Why put a reverse proxy (such as nginx or Envoy) in front of your app servers? easy Flashcard
  5. A load balancer uses sticky sessions, pinning each user to one server that keeps their session in memory. What is the main drawback? easy Multiple choice
  6. How does anycast send each user to a nearby server, and where is it used? medium Flashcard
  7. Why do services keep persistent, pooled connections to each other instead of opening one per request? medium Flashcard
  8. What do you trade when you lower a DNS record's TTL from an hour to 30 seconds? medium Flashcard
  9. When would you pick least connections over round robin for a load balancer? medium Flashcard
  10. A user is 150 ms (round trip) from your only data center. Over a new connection (TCP plus TLS 1.3), how long until the response to the first request arrives, ignoring server time? medium Estimate
  11. Service instances start and stop every few minutes as they autoscale. How do callers find the healthy ones? medium Multiple choice
  12. What do you gain, and what do you give up, by terminating TLS at the load balancer? medium Flashcard
  13. A user far from your origin requests a page the CDN has not cached. Why can the CDN still make it faster than going to the origin directly? hard Multiple choice
  14. GeoDNS answers each lookup with the address of the nearest region. What are its limits? hard Flashcard
  15. Before a client can send its first HTTPS request, a TCP handshake plus a TLS 1.3 handshake cost _____ round trips. QUIC (HTTP/3) combines them into _____. hard Fill in the blank
  16. Which problem does HTTP/3 (over QUIC) fix that HTTP/2 still has? hard Multiple choice

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