OLAP (Online Analytical Processing)

OLAP is the kind of database built for analysis rather than transactions: it answers big aggregate questions over millions or billions of rows — sums, averages, trends, breakdowns by category — usually for reports and dashboards. It is optimized for reading and summarizing huge amounts of data at once, not for tiny frequent edits.

OLAP systems often store data column by column (columnar storage) so that adding up one column across billions of rows is fast. The mental shorthand is simple: OLTP runs the business, OLAP helps you understand the business. Modern data warehouses are essentially powerful OLAP engines.