Databases

How this question breaks down

1. 1SQL vs NoSQLCore20 minRelational, document, key-value, wide-column and graph databases each make some questions cheap and others expensive, so the choice follows the queries you must answer and the facts that must never disagree.
2. 2IndexesCore19 minAn index is a sorted copy of some columns that turns a full-table scan into a handful of page reads, paid for on every write.
3. 3ReplicationCore27 minKeep copies of the database on several machines so it survives failures and serves more reads, and decide how long a write waits for those copies.
4. 4ShardingCore23 minSplit one dataset across machines by a partition key so that storage and writes grow with the fleet, and live with what that costs for queries that span keys.
5. 5TransactionsCore22 minGroup reads and writes so they commit or roll back together, and choose an isolation level that stops concurrent checkouts from corrupting each other.

Work through the parts in order and you’ve covered the full design. Each part is one topic.