Data and consistency

Where data lives and what a read is allowed to return: CAP, PACELC, partitioning, consistent hashing and choosing a database.

Oct 3, 2026databasesconsistency
Database indexing for system design interviews
Database indexing for system design interviews. What a B-tree buys you, why column order matters, and the write cost you name before you add another index.
Oct 3, 2026databasesconsistency
Database replication for system design interviews
Database replication for system design interviews. Why a second copy exists, sync versus async, what a reader may see, and a failover that avoids split brain.
Oct 3, 2026databasesconsistency
Quorum reads and writes in system design
Quorum reads and writes in system design. The inequality that keeps a quorum safe, sloppy quorums, and what you give up for extra availability.
Oct 2, 2026fundamentalsdistributed-systems
CAP theorem explained for interviews
CAP theorem explained for interviews. What the theorem actually says, why a partition forces a choice, and how to state it without the usual mistakes.
Oct 2, 2026fundamentalscachingdistributed-systems
Consistent hashing explained for the interview
Consistent hashing explained for the interview. Why hash-mod-N remaps most keys, how the ring moves about 1/N, and what virtual nodes are for.
Oct 2, 2026fundamentalsdistributed-systems
Database partitioning explained simply
Database partitioning explained simply. How to pick a shard key, what a hot key does, and how partitioning differs from a single replica.
Oct 2, 2026fundamentalsdistributed-systems
PACELC explained for system design
PACELC explained for system design. What the extra letter adds when the network is healthy, and how to choose latency or consistency on a whiteboard.
Oct 2, 2026fundamentalsdatabases
SQL vs NoSQL for system design interviews
SQL vs NoSQL for system design interviews. When a relational table is the right store, when a key-value or document store wins, and how to say the tradeoff.