How do slices differ from arrays in Go?
Assesses fundamental understanding of Go conventions, runtime behavior, and memory/performance considerations.
Hiring managers look for precision, avoidance of ambiguous jargon, and ability to explain trade-offs under real production conditions.
An array has a fixed length that is part of its type: [4]int and [5]int are different types, and copying an array copies all elements.
A slice is a small descriptor with three fields: a pointer to an underlying array, a length and a capacity. Slices are what you use almost everywhere because they can grow.
arr := [3]int{1, 2, 3} // array, fixed
sl := []int{1, 2, 3} // slice
sl = append(sl, 4) // grows, may reallocate
sub := sl[1:3] // shares the same backing array
Because sub shares memory, writing to sub[0] changes sl[1]. append reallocates when capacity is exceeded, so two slices can unexpectedly stop aliasing. Arrays are comparable with ==; slices are not comparable except to nil. Use arrays when the size is fixed and part of the contract, and slices for almost everything else.
Candidate Response Strategy & Interview Tips
- Start with a concise one-sentence summary: Deliver a direct, confident answer first before expanding into nuances.
- Demonstrate real-world trade-offs: Discuss where this approach excels and when you would avoid it in production systems.
- Discuss complexity & edge cases: Proactively explain time/space complexity or boundary conditions (null values, scale limits).
- Prepare for interviewer follow-ups: Technical hiring panels frequently probe deeper into concurrency, backward compatibility, or alternative libraries.