Slack has the best interview process I've been a part of.

My recruiter was highly transparent about what to expect each step of the way. I was told questions and disciplines I should prepare for, was given a practice repository with sample objectives to be ready for, etc.

After each step, I had a call with my recruiter. They would go over the feedback they received with me and tell me what the next steps would be and when to expect them.

What are you most proud of?

How do you manage juggling multiple projects/objectives?

What's the biggest bug you deployed to production, and how did you respond?

You are asked to take over an API. There is no documentation and no instrumentation. Recently, clients began reporting latency issues. What steps would you take in this situation?

Slack has an @ feature where you can tag users. If you were to design an API for it, what parameters would it accept? What would the response data look like?

You are given a code review (administered by HackerRank). Assume it is from a junior engineer, and you are the senior engineer for the team. Perform a code review.

What is the best team you've ever worked on, and why?

What was a time you were collaborative and delivered a big feature?

Tell me about a time you caused a production outage. What did you learn?

Where is the line for a developer's testing responsibilities? How does this change with or without a QA team supporting you?

Tell me about a time you had difficulties working with someone. How did you resolve it?

[Coding Interview] Given a fork similar to a simplified version of Slack's codebase, implement a series of requirements to enable private channels.

[System Design] Design a system to deliver globally unique identifiers at a massive scale.