I applied online. The process took 1 week. I interviewed at Paytm (Bengaluru) in Oct 2018
Interview
Onsite interviews were purely technical. First-round focused on the basics of iOS, Swift and Objective C, Memory Management.
I was asked to design/write architecture for an app. I covered every topic from architecture, networking, security, data caching, image caching, database, queuing, iOS extensions, threading etc.
Third round focused covered all the concepts from my design in depth.
The final onsite interview was with a tech lead from Paytm money. We discussed about iOS architectures, dependency injection, testing. He covered network layer in depth and also asked how would I implement an animation.
The final round was telephonic with AVP.
Great interview!
I applied through a recruiter. The process took 2 weeks. I interviewed at Paytm (Gurgaon, Haryana) in Jun 2020
Interview
Paytm HR contacted me through call after visiting my profile on LinkedIn. They were looking for 2-3 experienced iOS developer. There were 4 rounds in total. Whole process took less than two weeks. In first round, I was asked two coding problems and basic swift questions. Coding problems were of easy difficulty. This was an easy round. HR was very swift and declared the result on the same day only. Second round was most interesting round of all. It involved discussion over architecture patterns and design patterns. We literally fought over how would I manage caching in app. Interviewer was very understanding though and appreciated my reasoning. In third round, one medium level coding problem and some swift related questions were asked. Also I had to explain high level class diagram for a feature. These rounds were of easy to medium difficulty. Fourth round was toughest of all. I was asked to write a class that will replicate the caching mechanism. Class should have utility function to get, set and remove cache data for a key, store the data values in file directory and automatically deallocate memory after certain memory threshold is reached. I had mentioned that I know a bit of backend too, so was asked questions about RESTful APIs and how do I develop APIs. Interviewer also asked me about RabbitMQ and load balancers, what all features I've developed in app end to end and explain any one in detail.
Interview questions [3]
Question 1
nonescaping vs escaping closure, class vs structs - what to use when, lazy keyword, dispatch queues, thread management etc. Sort array of 0s and 1s in O(n). If sum of any two elements of array results in given value.
MVC vs MVVM - how do you decide which to use when. What all design patterns have you used. Questions about iterator, decorator and singleton pattern. What points you'll consider while designing your network layer. Why swift is called protocol oriented language. Why it's made protocol oriented and not object oriented.
Find next greater element for each element in an array in O(n). How would you implement a feature that involves fetching thousand of images through network call and displaying them in collection view. Caching types available in swift and their use cases. Thread management.