Hey Community,
I’m currently working as an SDE-2, and recently had the opportunity to interview with Allen Digital for a Backend SDE-2 role. I applied through LinkedIn.
Round 1 (Machine Coding) – Cab Driver Billing System
Problem Statement:
You are part of a cab aggregator company, Allen Cabs, similar to Ola/Uber. As part of the Driver Billing team, you need to build a system that periodically generates bills for drivers based on the distance they've driven.
Platform Capabilities:
Drivers are onboarded to Allen Cabs and assigned a unique ID.
Vehicles are classified into three categories based on their model:
Economy
Premium
Luxury
Billing is based on the distance driven during trips, which can be:
Intra-city
Outstation
Billing Rates:
Intra-city:
Economy – ₹5/km
Premium – ₹12/km
Luxury – ₹15/km
Outstation: Charges are 2x of intra-city rates.
Cancellation Policy:
If a driver cancels the trip → fine of ₹10.
If a customer cancels the trip → driver is compensated ₹10.
Bonus Requirements (optional):
Variable cancellation fee based on trip type and vehicle category.
Ability to generate bills for a given time interval.
Drivers can either use:
Personal vehicles, or
Leased vehicles (leased from Allen Cabs, Allen charges x% of the bill as commission).
Method Signatures & Sample Inputs
AddDriver
AddDriver("Sachin", "+91-9936673000", "D101")
AddDriver("Ramesh", "+91-9936673011", "DL_02")
AddDriver("Manjunath", "+91-9936673010", "DL_03")
AddVehicle
AddVehicle("KA-01-2222", "Maruti Suzuki", "ECONOMY")
AddVehicle("KA-01-2223", "Ertiga", "PREMIUM")
MapDriverToVehicle
MapDriverToVehicle("Ramesh", "KA-01-2222")
MapDriverToVehicle("Manjunath", "KA-01-2223")
AddTrip
AddTrip(50, 1723116023, 1723117023, "INTRACITY", "COMPLETED", "Ramesh")
AddTrip(1050, 1723116023, 1723117023, "OUTSTATION", "COMPLETED", "Ramesh")
AddTrip(50, 1723116023, 1723117023, "INTRACITY", "CANCELED_CUSTOMER", "Ramesh")
AddTrip(50, 1723116023, 1723117023, "OUTSTATION", "CANCELED_DRIVER", "Manjunath")
AddTrip(70, 1723116023, 1723117023, "OUTSTATION", "COMPLETED", "Manjunath")
GetBill
GetBill("Ramesh") => (50 * 5) + (1050 * 10) + 10 = ₹10,560
GetBill("Manjunath") => -10 + (70 * 12 * 2) = ₹1,670
I was able to pass all test cases. For the bonus requirements, I discussed my approach with the interviewer, and he seemed satisfied with the direction I took.
Round 2 (DSA)
Search in Rotated Sorted Array - https://leetcode.com/problems/search-in-rotated-sorted-array/description/
Meeting Rooms II - https://leetcode.com/problems/meeting-rooms-ii/description/
I solved both problems starting from the brute-force approach and then optimized them step-by-step. These are fairly common problems and I was well-prepared for them.
Round 3 (HLD + LLD)
The interviewer was quite experienced. We began by discussing my previous projects and work experience. Then, I was asked to design a Ticket Booking System similar to IRCTC.
Here’s what I covered:
Identified and discussed core entities and their relationships.
Asked for and incorporated the interviewer’s feedback throughout the discussion.
Transitioned into the High-Level Design, covering components and request flow.
Toward the end, I was asked to add support for User Preferences (like berth choice).
I discussed possible design patterns that would allow such changes to be accommodated in a scalable and maintainable way.
The interviewer seemed satisfied with my design and thought process.
Final Result
Unfortunately, despite multiple follow-ups with the TA Coordinator, I never received any concrete feedback. The only response I got was:
“I’ll get back to you soon.”
Hope this post helps others preparing for backend interviews!