What is ACID vs BASE?

A - Atomicity: All or nothing transactions
C - Consistency: Valid state after transaction
I - Isolation: Transactions don't interfere
D - Durability: Committed data persists

// Bank transfer - must be atomic
BEGIN TRANSACTION;
  UPDATE accounts SET balance = balance - 100 WHERE id = 1;
  UPDATE accounts SET balance = balance + 100 WHERE id = 2;
COMMIT;
// Either both succeed or both fail

BA - Basically Available: System always responds
S  - Soft state: State may change over time
E  - Eventual consistency: Eventually consistent

// Social media like count
// May show 999 likes briefly before updating to 1000
// Eventually correct, but not immediately

// ACID for multi-document transactions
session.withTransaction(async () => {
  // ACID guarantees here
});

// BASE for single documents (default)
db.metrics.insertOne({ views: 1 });