Call from recruiter, followed by a 45-minute call with a technical person.
Questions covered memory, threading, and UI.
I answered most of the questions.
Subsequently, I received a call from the recruiter informing me that they are looking for more senior developers.
Explain memory management and threading.
And couple UI related questions.
The following metrics were computed from 1 interview experience for the Slack Senior iOS Developer role in Canada.
Slack's interview process for their Senior iOS Developer roles in Canada is extremely selective, failing the vast majority of engineers.
Candidates reported having very negative feelings for Slack's Senior iOS Developer interview process in Canada.

