Kakao Engineer Deep Dive into MongoDB WiredTiger File Structure

As the first installment of the 'MongoDB WiredTiger File Structure' series on the Kakao Tech Blog, this post analyzes the internal structure of key files managed by WiredTiger. The history store (WiredTigerHS.wt), introduced in WiredTiger 10.0.0, stores past version data from memory for MVCC and replaces the legacy WiredTigerLAS.wt file. The journal logs (journal directory) serve as a Write-ahead log, ensuring data durability during abnormal terminations; the example demonstrates that insert, update, and delete operations are all recorded as row_put types. Additionally, the post examines the mapping information between MongoDB namespaces and WiredTiger internal identifiers (ident) and the index metadata structure via the _mdb_catalog.wt file.