Traffic puzzle
Keep app servers replaceable
A notification API gets bursty mobile traffic during live sports events.
Puzzle target
Route traffic through replaceable services without keeping user state on one server.
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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: Load Balancing and Stateless Services?
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 | Split traffic across stateless application workers and keep sticky state out of the service tier. |
Practice Task
- Place the load balancer, app servers, cache, and database in the request path.
- Use the design puzzle below to choose components and tradeoffs.
- Explain the bottleneck before adding more infrastructure.