Model puzzle
Shape APIs and entities
Design comments on posts with edit history, moderation decisions, and author deletion.
Puzzle target
Choose an API/data path that preserves the important relationships without hiding consistency needs.
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Complete each design choice to unlock the review. The feedback above will point out what your current tradeoff misses.
Flash cards
Review the key moves
What is the main idea behind System Design: API and Data Model?
Lesson checks
Practice each idea before moving on
Short Mimo-style checks built from this lesson's code, terms, and sequence.
Which statement best captures the main point of this lesson?
Put the learning moves in the order that makes the concept easiest to apply.
System design is a sequence of explicit tradeoffs. Start small: clarify the goal, estimate load, pick the simplest architecture, then name what breaks first.
| Design surface | What you decide |
|---|---|
| Requirements | Functional behavior, constraints, and non-goals |
| Scale | Reads, writes, storage, bandwidth, and latency target |
| Architecture | Clients, load balancer, services, cache, database, queue, and workers |
| Reliability | Failure mode, fallback, retry, and metric |
| Goal | Choose API boundaries and the core entities before talking about scaling. |
Practice Task
- Define the main read/write APIs, primary keys, indexes, and the data that must stay consistent.
- Use the design puzzle below to choose components and tradeoffs.
- Explain the bottleneck before adding more infrastructure.