Type · algorithms
Walk me through how you would design an algorithm to find the maximum overlapping symptom intervals for a user logging periodic health symptoms over a multi-month period.
How to Pass the Flo Software Engineer Interview in 2026
Growth · Software Engineer Interview Guide
Sign up to see ATSHeadquartered in United KingdomInterview language: English
The Flo DNA (TL;DR)
Medical accuracy and user trust in Flo's ovulation tracking drive evaluation metrics. Interviewers test whether candidates can scale engagement across sensitive health logging features while maintaining strict compliance with medical review board standards.
The Flo Interview Loop
Your onsite loop will typically consist of 5 rounds.
- 1
Round 1
Recruiter ScreenMotivation, role fit, logistics. - 2
Round 2
Coding ScreenLeetCode-medium algorithmic problems under time pressure. - 3
Round 3
System DesignDistributed systems, trade-offs at scale, architecture under constraints. - 4
Round 4
Onsite CodingLeetCode-hard problems, reasoning about defects, code clarity, edge cases. - 5
Round 5
Behavioral / LeadershipPast evidence of ownership, influence, resolving conflict.
The Danger Zone: Top Reasons Candidates Fail
Based on our database of Flo interview outcomes, avoid these common traps:
- Failing to partition storage based on high write volume
- Suggesting crude global lock barriers that freeze the client application UI thread
- Storing every raw timestamp in unbounded memory arrays causing memory leaks at scale
- Proposing full dataset transfer instead of computing incremental diffs
Test Yourself: Real Flo Questions
Three real prompts pulled from our database.
Type · coding-onsite
Design and implement a data structure that supports inserting period prediction windows and efficiently querying whether a given date falls within any high-confidence prediction interval.
Type · system-design
Design an offline-first backend synchronization engine for a global health app with 50+ million active users subject to intermittent connectivity.
+ many more questions, signals, and worked examples
Sign up to unlock the full Flo grading rubric
Flo Interview Question Bank
A sample from our database, grouped by round. Sign up to see the full set.
7 of 15 questions shown
1
Recruiter Screen
1- 1
Type · recruiter-screen
Why Flo Health, and how has your software engineering background prepared you to work on high-concurrency mobile backends with strict health data privacy standards?
2
Coding Screen
4- 2
Type · algorithms
Walk me through how you would design an algorithm to find the maximum overlapping symptom intervals for a user logging periodic health symptoms over a multi-month period. - 3
Type · algorithms
How would you implement an in-memory token bucket rate limiter to protect sensitive health data telemetry endpoints from client retry storms? - + 2 more questions in this round (sign up to unlock)
3
System Design
5- 4
Type · system-design
Design an offline-first backend synchronization engine for a global health app with 50+ million active users subject to intermittent connectivity. - 5
Type · system-design
Design an anonymized health insights analytics system that computes population-level cycle statistics without risking individual user identification. - + 3 more questions in this round (sign up to unlock)
4
Onsite Coding
5- 6
Type · coding-onsite
Walk me through how you would identify and fix a multi-threading race condition in a local queueing system where offline user health logs are flushed concurrently during background app refresh and manual user submission. - 7
Type · coding-onsite
Design and implement a data structure that supports inserting period prediction windows and efficiently querying whether a given date falls within any high-confidence prediction interval. - + 3 more questions in this round (sign up to unlock)
Unlock all 15 Flo questions, free
No credit card. Every question with its framework, the grading signals interviewers score against, and a worked answer for each.
Interview tracks at Flo
How Flo's DNA translates across functions. Pick your role.
Compare Flo with similar employers
Same DNA, different bar. Browse the closest companies in our database and see how their loops differ.
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Practice Flo interviews end-to-end
Flo Mock Interview
Run a live mock interview with our AI interviewer using Flo-style prompts. Get scored on structure, signal, and answer length - exactly how the real loop grades you.
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STAR Stories for Flo Behavioral Rounds
Build a Story Bank of your past wins, mapped to the leadership signals Flo interviewers grade on. Reuse them across every behavioral round.
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Flo Interview Prep Hub
The frameworks behind every Flo round: CIRCLES for product sense, hypothesis-driven debugging for analytical, STAR for behavioral. Learn each one in 10 minutes.
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Interview Frameworks
CIRCLES, STAR, AARRR, RICE, MECE. The exact frameworks that make Flo interviewers nod instead of frown. Step-by-step playbooks with the moves and the pitfalls.
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Sample answers
What a strong answer to these Flo interview questions shows.
Walk me through how you would design an algorithm to find the maximum overlapping symptom intervals for a user logging periodic health symptoms over a multi-month period.
A strong answer shows: Mastery of interval algorithms and sweep-line technique; Ability to analyze computational complexity clearly; Attention to edge cases in continuous vs discrete timeline inputs.
Design and implement a data structure that supports inserting period prediction windows and efficiently querying whether a given date falls within any high-confidence prediction interval.
A strong answer shows: Ability to implement specialized tree structures for range queries; Methodical handling of edge cases in date and time ranges; Clean, maintainable object-oriented or functional implementation.
Frequently asked questions
How long does the Flo interview process take?
Most candidates spend between 4 and 8 weeks from recruiter screen to offer. The onsite loop itself runs in a single day or is split across two half-days, with debrief and offer typically within 5 business days after.
How should I prepare specifically for Flo?
Focus on three things: (1) the company DNA shown above - what they actually grade for, (2) the rounds in your loop, especially the round most candidates underestimate, and (3) drilling on the question types in this guide using a structured framework like CIRCLES or STAR.
Does this apply to engineering or design roles at Flo?
The DNA stays the same - what changes is the round mix. SWE candidates face coding screens instead of Product Sense; designers face portfolio reviews and design exercises. The "what they value" and behavioral signals carry across all functions.
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