Concurrency

/reɪs kənˈdɪʃən/

noun — "outcome depends on timing, not logic."

/ˌmʌltiˈprəʊsɛsɪŋ/

noun … “Multiple processes running in parallel.”

/ˈθrɛdɪŋ/

noun … “Parallel paths of execution within a program.”

/ˌɛm viː siː ˈsiː/

n. — "Database sorcery keeping readers blissfully ignorant of writers' mayhem."

MVCC (Multi-Version Concurrency Control) stores multiple temporal versions of each database row, letting readers grab consistent snapshots without blocking writers—who append fresh versions instead of overwriting. Unlike 2PL locking wars, transactions see "their" reality via timestamps/transaction IDs, with garbage collection culling ancient corpses once safe.

Key characteristics and concepts include: