Expense sharing

Why it matters

Explain the problem expense sharing addresses and where it shows up in real code.

The idea

The core mechanism, with one diagram.

Trade-offs

What you give up, and the failure modes to name before an interviewer asks.

In an interview

How to bring it up, how deep to go, and the follow-up questions to expect.

Key takeaways

• One sentence you can say out loud.
• When to reach for it, and when not to.
• The neighbouring topic to connect it to.