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From ACID to Sagas- Strong Inside, Coordinated Outside -Distributed Transactions in Banking
Strong Internal Consistency, External Coordination: Distributed Finance Explained
Sudha Subramaniam5 min read·Just now--
Two accounts. One database. One local transaction.
Debit one row. Credit another row. If anything fails — rollback.
Life is predictable.
Inside a single system, atomic transactions give you safety. The database guarantees consistency. Either both operations succeed, or neither does.
But then reality changes the boundaries.
Account A is in Bank A.
Account B is in Bank B.
Different databases. Different infrastructure. Different data centers. Different companies.
There is no shared transaction manager. There is no global lock. There is no magical distributed @Transactional.
This is where distributed systems begin — and where simple single-database assumptions no longer apply.
What This Story Will Cover
In this article, we’ll walk through how distributed transactions actually work in modern banking systems.
Specifically, we’ll explore:
- How ACID guarantees work inside a single bank
- Why traditional distributed commit protocols are hard to apply across separate…
