Data Structures & Algorithms
Also written as DSA
The foundational computer-science toolkit — arrays, trees, graphs, hash maps, sorting, recursion — for reasoning about how code performs as data grows. The subject matter behind most whiteboard-style technical interviews, regardless of what the job itself actually involves day to day.
Think of it like
Like a chef's knowledge of ingredient properties and technique — versus the actual recipes (frameworks, tools) used on the job.
Junior or senior?
Junior sounds like
Treats DSA fluency as proof of production ability on its own.
Senior sounds like
Can describe a time picking the right data structure — not just the right framework — measurably fixed a real performance problem.
Ask them
“Tell me about a time picking the right data structure — not just the right framework — measurably fixed a performance problem.”