Consistency & Trade-offs
When the network splits, you choose what breaks. Know what you're choosing.
5 lessons · ~51 min · free
By the end you can
- State CAP precisely, including why partition tolerance isn't optional
- Tell strong from eventual consistency with concrete user-visible symptoms
- Reason about N/R/W quorums and what overlap buys you
- Fix read-your-writes problems with routing and session guarantees
- Choose consistency per feature, and defend the choice in an interview
Lessons
- 1The cable gets cut10 minTwo datacenters, one partition, and the forced choice CAP is actually about.
- 2Strong vs eventual, in symptoms11 minWhat each guarantee means for a user mid-click, and the cost of promising more.
- 3Agreeing without everyone11 minN, R, and W: why overlap gives you your write back, and the dials between fast and safe.
- 4At least see your own writes10 minRead-your-writes and monotonic reads: the small promises that fix the embarrassing bugs.
- 5Consistency is a per-feature choice9 minBalances strong, like-counts eventual: the decision framework and the interview vocabulary.
Design with it after
The design library has full system design prompts on a whiteboard canvas with AI feedback. Every one of them gives you a place to apply this.
Open the design library