Design a Time-Travel Query System

Concepts: pyTimeTravel, pyMVCC, pyDeltaLake, pyVersionLog

Time travel queries -- 'give me the state of this dataset at timestamp T' -- are a staff-level design question that appears in interviews at Databricks, Snowflake, Meta, and similar companies. The underlying mechanism is almost always binary search on a sorted version log. Understanding this at the implementation level, and connecting it to Delta Lake, MVCC, and snapshot isolation, demonstrates the kind of systems depth that earns 'strong hire' at the senior and staff levels. The Version Log A version log is an append-only list of commits, each with a monotonically increasing timestamp (or version number) and a pointer to the state of the dataset at that version. Finding the state at timestamp T requires finding the latest commit with timestamp <= T. This is a last-occurrence binary search