Day 53 drills

Paper first. Warm-up before the two timed runs.

D1 (rate limiter: why a local-only bucket on each of ten gateways breaks a 100/min limit, and the two fixes with their costs):

D2 (rate limiter: which algorithm and why, and exactly what you return to a rejected client):

D3 (news feed: fan-out on write vs on read in one sentence each, and the cost that kills each at the extreme):

D4 (news feed: the hybrid, who gets which, and how one follower’s feed is assembled from both):

D5 (both: the central store goes down for the limiter, and a celebrity posts, what you do in each case):