Type Alias: Purpose

Purpose = "metadata" | "data"

Defined in: types.ts:11

What a read is for. Metadata is what a format reads before it can ask for data and what every later read depends on: a COG's IFDs and offset tables, a sharded Zarr shard's index, a PMTiles directory. Data is the payload: tiles, chunks. The two are merged separately, metadata reads are widened to blocks, and each counts against its own cache budget, so data churn never evicts the small structural reads.