Data engineering interviews include coding:
Aggregation with grouping:
df.groupby('user_id').agg(
total_orders=('order_id', 'count'),
total_spent=('amount', 'sum'),
avg_order=('amount', 'mean')
)
Window functions:
df['running_total'] = df.groupby('user_id')['amount'].cumsum()
df['rank'] = df.groupby('category')['sales'].rank(ascending=False)
Merging and joining:
result = orders.merge(customers, on='customer_id', how='left')
Practice these patterns until they're automatic. Your interviewer expects fluency.