Code RoomParquet schema evolution
MediumPrep Room Coding #3317

Parquet schema evolution

System designDatabases & SQLMid–Senior~40 min

A data lake stores 5 years of event data as Parquet in a lakehouse table queried by Spark and Trino. Product needs ongoing schema changes: add columns, rename a column, change a column's type (int→bigint, string→struct), and reorder columns — without rewriting all 5 years of files and without breaking old queries or jobs that read older partitions. Files written under old schemas must still be readable alongside new ones. Design how the table handles schema evolution so reads stay correct across schema versions.

What a strong answer looks like

Clarify scale and constraints first. Propose a clean component breakdown, then go deep on the hard parts (data model, bottlenecks, consistency, failure modes) and name the trade-offs you are making.

Clarify4:30 left
Estimate4:30 planned
Design13:30 planned
Deep dive10:30 planned
Failure7:00 planned
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Which questions mattered is sealed until you submit. Telling you now would just be handing over the edge cases.