Eightfold.AI Lead Backend (SDE-3) Interview Experience
- Posted
- 23 Mar 2026
Summary
I interviewed for a Lead Backend (SDE-3) Engineer role at Eightfold.AI, which involved discussions on past projects, behavioral questions, a coding problem on stream processing for unique elements, and a system design problem.
How it went
Sharing my interview experience for SDE-3(lead) engineer role at Eightfold.ai
Round 1: HM
Mostly discussed around past projects, your contribution and behavioral questions
Round 2: Coding + HLD
You receive strings one by one from a stream.
After each insertion, you must output:
the oldest string that has appeared exactly once so far
If no such string exists, return ""
Example
Stream:
a, b, a, c, b, d
After each insert:
insert a → oldest non-repeating = a
insert b → a
insert a → b
insert c → b
insert b → c
insert d → c
Output:
a, a, b, b, c, c
For HLD : Design Notification Service.
Questions asked (2)
- 01
Oldest Non-Repeating String in Stream
Data Structures & Algorithms
You receive strings one by one from a stream.
After each insertion, you must output:
the oldest string that has appeared exactly once so far
If no such string exists, return ""
Example
Stream: a, b, a, c, b, d After each insert: insert a → oldest non-repeating = a insert b → a insert a → b insert c → b insert b → c insert d → c Output: a, a, b, b, c, c
- 02
Design Notification Service
System Design
Design Notification Service.