Design a URL Shortener
A classic warm-up problem precisely because it's small enough to fully design in an interview, while still forcing real decisions about ID generation, read/write ratios, and caching — following the six-step framework from How to Answer a System Design Interview Question.
Design a Rate Limiter
Rate Limiting covered the algorithms (token bucket, sliding window) in the abstract; this problem is about actually building the service that enforces them — specifically, where the counters live and how they stay correct when many application servers are checking and updating them concurrently. Following the framework from How to Answer a System Design Interview Question.
Design Pastebin
Pastebin looks almost identical to Design a URL Shortener on the surface — a short code maps to something bigger — but the "something bigger" is the whole difference: a URL shortener stores a tiny string, while Pastebin stores arbitrarily large blocks of text. That single change pushes the interesting design decision from "how do I generate the short code" to "where does the actual content live." Following the framework from How to Answer a System Design Interview Question.
Design a Key-Value Store
This is the problem where nearly every Database Fundamentals and Distributed Systems lesson in this course gets applied at once — a distributed key-value store is the classic Dynamo/Cassandra-shaped design, and it's included as an "easy" problem here specifically because most of its hard sub-problems already have their own dedicated lessons to draw on directly. Following the framework from How to Answer a System Design Interview Question.
Design a Parking Lot System
A deliberately different kind of "easy" problem from the rest of this section multiple entry gates trying to assign a spot to different cars at the same instant must never assign the same spot twice. Following the framework from How to Answer a System Design Interview Question.