Part 4 of 8 · week 4 of the learning path

When data volume, speed or complexity is the main challenge, the design comes down to four choices: how data is stored, copied, split and kept consistent.

Learning objectives

Choose a storage engine and data model for a workload.

Reason about replication, partitioning and the anomalies they create.

Pick transaction and consistency levels, and decide between batch and stream processing.

Storage

Choice Strength Used by

B-tree Updates in place, fast reads, mature indexing Most relational databases

LSM-tree Fast writes through sequential appends and background compaction Cassandra, RocksDB and similar

Row store Whole-record reads and writes (OLTP) Application databases

Column store Scanning a few columns over many rows (OLAP) Warehouses and analytics

Replication

Leader and followers: writes go to the leader and copy to followers, synchronously or asynchronously; simple and common.

Multi-leader: several leaders accept writes, useful across regions, but…