Normalization / Denormalization
Also written as DB Normalization
Normalization organizes a relational database to minimize duplicate data (splitting it across related tables); denormalization deliberately duplicates some data back to make reads faster, at the cost of more complex writes.
Think of it like
Normalization is like keeping one master copy of a customer's address on file and referencing it everywhere; denormalization is like printing that address on every single receipt so the cashier never has to look it up.
Junior or senior?
Junior sounds like
Normalizes everything by default without considering read cost.
Senior sounds like
Can describe a specific table they deliberately denormalized for read performance, and what it cost them on writes.
Ask them
“Tell me about a table you deliberately denormalized. What read performance did it buy you, and what did it cost on writes?”