Chapter 3 checkpoint

Chapter 3 checkpoint: edge routing and security

Every question from this chapter’s lessons. Your first answer to each is the one that counts; afterward you can practice again as often as you like. Passing needs 75% right on the first attempt.

0 of 17 answered0 right on the first attempt

Question 1 of 17

Next week you will move a service to a new IP address, and its DNS record has a 24-hour TTL. What should you do with the TTL?

Leave it; DNS changes are immediateRaise it so resolvers ask less oftenLower it at the moment you switch the addressLower it to about a minute well before the move, then raise it again afterward

Question 2 of 17

Match each DNS record type to what it holds.

AAAAACNAMEMX

Question 3 of 17

You want 10% of users to reach a new canary cluster while 90% stay on the current one. Which DNS routing policy do you use?

Weighted routingLatency-based routingFailover routingGeolocation routing

Question 4 of 17

A service uses one anycast address announced from many sites. Users in one city are served by a site with a longer round-trip time than another site that is also announcing the address. Why can this happen?

The DNS answer for the address has expiredGeolocation routing is misconfiguredInternet routing picks the nearest site in routing terms, which is not always the fastestThe faster site must be failing its health checks

Question 5 of 17

A media service gets 10,000 read requests per second, and each response is 200 KB. With a CDN in front achieving a 90% hit ratio, how much bandwidth still reaches the origin, in MB/s?

Your answer

Answers within 5% count, in any unit you choose.

Question 6 of 17

A small site gets little traffic, and its content rarely changes. Which kind of CDN does the lesson say works well for it?

A pull CDNA DNS cache instead of a CDNA push CDNNeither: CDNs only help dynamic content

Question 7 of 17

Match each Cache-Control directive to what it does.

max-ages-maxagestale-while-revalidateimmutable

Question 8 of 17

An API whose responses are never cached gets noticeably faster for distant users after it is put behind a CDN. How?

The CDN lowers the DNS TTLCDNs make the origin compute responses fasterThe CDN caches the API responses anywayHandshakes complete with a nearby edge, which reuses its connection to the origin

Question 9 of 17

Which job calls for a layer 4 load balancer rather than a layer 7 one?

Keeping users on the server named in a session cookieSpreading a custom TCP protocol across servers at the lowest cost per connectionSending /video requests to video serversRouting on an HTTP header such as Host

Question 10 of 17

Match each routing method to how it picks a server.

Round robinWeighted round robinLeast connectionsIP hash

Question 11 of 17

Under round robin, some requests take seconds and others milliseconds, and one server often ends up with a pile of slow requests while others sit idle. Which routing method fixes this?

RandomLeast connectionsIP hashWeighted round robin

Question 12 of 17

What changes with direct server return?

The load balancer terminates TLS for the serversServers send responses straight to the client, bypassing the load balancerDNS returns each server’s address directlyClients send requests straight to the servers

Question 13 of 17

A token bucket holds at most 50 tokens and gains 10 tokens per second. It starts full. At most how many requests can it admit during the first 3 seconds?

Your answerrequests

Answers within 2% count.

Question 14 of 17

What is the main benefit of terminating TLS at a reverse proxy?

The site no longer needs a certificateBackend servers no longer do the potentially expensive encryption and decryptionTraffic between the proxy and the backends is automatically encryptedDatabase queries run faster

Question 15 of 17

You want to let a client make a short burst of requests while capping its long-run average rate. Which rate-limiting algorithm fits?

A web application firewallToken bucketDirect server returnLeaky bucket

Question 16 of 17

Which component applies rules to HTTP traffic to block a request containing ' OR 1=1--?

A rate limiterA web application firewallA layer 4 load balancerA CDN

Question 17 of 17

Images of 100 KB each are requested 20,000 times a second. The CDN answers 90% from its edge caches and fetches each miss from the origin. Which component saturates first?

CDN edgeServes up to 200,000 requests/s

Origin uplink1 Gbit/s

Origin servers ×4Each handles 1,000 requests/s

Object storageServes up to 10,000 reads/s