Went through Slack's coding interview process recently and want to document what I saw because info online is all over the place.
First: there is NO traditional timed OA (online assessment) at the start, at least for the SWE roles I applied to (L4/L5 track). Instead you do a 45-minute coding round with a live interviewer on CoderPad. No lockdown browser, no camera required.
The problem I got was graph traversal. BFS variant with some business logic layered on top. Medium-hard on LeetCode scale. Nothing that requires memorizing DP patterns, but you do need to be comfortable with recursion and knowing when to reach for a queue vs. a stack.
Pace was relaxed. Interviewer let me think out loud. I asked if I could start with a brute-force approach and they said yes, just flag it. After the working solution they asked about time complexity and whether the approach would change if the input size scaled 100x. That's almost always where the follow-up lives.
Tips from my own prep: Do Slack-tagged problems on Leetcode (not many, but they repeat) Practice talking while coding. Silent sprints won't cut it here Know your hash maps and how to use them to avoid O(n^2) solutions For L5 especially: be ready to discuss edge cases unprompted
One thing I noticed: the interviewer took notes actively, more than most. They seem to care about the communication dimension of the round, not just whether you got the right answer.
The overall loop has one coding round, so this is your one shot. Don't underestimate it because Slack is "less FAANG." The bar is real.