Pattern Path
Know the next problem.
Pick an engine and follow it step by step. Every step is one problem shape, with an anchor problem to learn it, variations to practise it and twists that break the obvious answer.
SQL
From filtering rows to reading a query plan, one problem shape at a time.
18 steps
Python
The Python that data engineering interviews ask for, with the algorithms branch kept optional.
12 steps + 7 optional
PySpark
DataFrames, joins, windows, skew and pipelines in the order you meet them.
15 steps
Pandas
Load, clean, reshape and validate tables in pandas.
8 steps