Welcome to your interview.
The question is on your right: Explain ACID in Transaction Systems. Take a moment with it first.
Talk your thinking through with me if you like - when you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes). Discussion and graded submissions share your five interviewer interactions, so spend them well.
ACID is a core database concept that matters whenever you work with transactional data such as payments, account balances, or statement updates. In analytics and operational systems, understanding ACID helps you reason about correctness when multiple writes happen at the same time.
You are asked to explain the four ACID properties in a relational database. Define Atomicity, Consistency, Isolation, and Durability, and describe what each one guarantees during a transaction. You should also explain why these properties matter in a payment or ledger-style workflow, such as updating balances for an American Express card account.
Keep your answer at an interview level: give clear definitions, a practical example for each property, and mention at least one common misconception or trade-off, especially around isolation and consistency.