Type · Debugging
A Freebox router is intermittently dropping internet connections for users in a specific building. The logs show occasional 'DHCP lease renewal failures'. Debug this issue, identify potential root causes, and propose a fix.
How to Pass the Iliad / Free Software Engineer Interview in 2026
The Iliad / Free DNA (TL;DR)
The hiring managers at Iliad / Free seek individuals who can pragmatically innovate, especially in disrupting telecom norms exemplified by Free Mobile. They look for direct, cost-effective solution generation, aligning with Xavier Niel's vision for lean, impactful operations.
The Iliad / Free 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, debugging, 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 Iliad / Free interview outcomes, avoid these common traps:
- Blaming the other party or portraying them as unreasonable without acknowledging their perspective.
- Focusing on authority or pressure rather than persuasion.
- Inefficient parsing logic, leading to slow processing of large log files.
- Jumping to conclusions without analyzing relevant logs (router, ISP, client devices).
Test Yourself: Real Iliad / Free Questions
Three real prompts pulled from our database.
Type · Data Structures
Design a system to efficiently track and report the number of active mobile users within specific geographic regions (e.g., cities, neighborhoods) in real-time. Assume data streams from millions of devices.
Type · Data Storage
Design a database schema and strategy for storing customer call detail records (CDRs) for Iliad. Consider the massive scale, the need for efficient querying (e.g., by customer ID, time range, call type), and data retention policies.
+ many more questions, signals, and worked examples
Sign up to unlock the full Iliad / Free grading rubric
Iliad / Free Interview Question Bank
A sample from our database, grouped by round. Sign up to see the full set.
9 of 20 questions shown
1
Recruiter Screen
1- 1
Type · Motivation
Why are you interested in joining Iliad/Free, and what excites you about working in the telecom industry specifically?
2
Coding Screen
3- 2
Type · Algorithmic
Given a list of cell tower locations (latitude, longitude) and a user's current location, find the N closest cell towers. Consider the Earth's curvature for distance calculation. - 3
Type · Data Structures
Design a system to efficiently track and report the number of active mobile users within specific geographic regions (e.g., cities, neighborhoods) in real-time. Assume data streams from millions of devices. - + 1 more questions in this round (sign up to unlock)
3
System Design
3- 4
Type · API Design
Design an API for a new Iliad service that allows users to remotely manage their Freebox settings (e.g., Wi-Fi password, port forwarding). Consider security, scalability, and ease of use for developers integrating with it. - 5
Type · Scalability
How would you design a system to handle the signaling traffic for Iliad's mobile network, ensuring low latency and high availability, especially during peak hours or major events? - + 1 more questions in this round (sign up to unlock)
4
Onsite Coding
3- 6
Type · Algorithmic (Hard)
You are given a list of network connection events, each with a start time, end time, and source/destination IP addresses. Find the longest period during which a specific IP address was continuously connected to the network, possibly through multiple intermediate hops. - 7
Type · Debugging
A Freebox router is intermittently dropping internet connections for users in a specific building. The logs show occasional 'DHCP lease renewal failures'. Debug this issue, identify potential root causes, and propose a fix. - + 1 more questions in this round (sign up to unlock)
5
Behavioral / Leadership
10- 8
Type · conflict resolution
Tell me about a time you had a significant disagreement with an engineer or designer about a product decision. How did you approach it, and what was the outcome? - 9
Type · ownership
Describe a time you took ownership of a project or problem that was outside your direct responsibility. What motivated you, and what did you achieve? - + 8 more questions in this round (sign up to unlock)
Unlock all 20 Iliad / Free 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 Iliad / Free
How Iliad / Free's DNA translates across functions. Pick your role.
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Practice Iliad / Free interviews end-to-end
Iliad / Free Mock Interview
Run a live mock interview with our AI interviewer using Iliad / Free-style prompts. Get scored on structure, signal, and answer length - exactly how the real loop grades you.
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STAR Stories for Iliad / Free Behavioral Rounds
Build a Story Bank of your past wins, mapped to the leadership signals Iliad / Free interviewers grade on. Reuse them across every behavioral round.
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Iliad / Free Interview Prep Hub
The frameworks behind every Iliad / Free 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 Iliad / Free 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 Iliad / Free interview questions shows.
A Freebox router is intermittently dropping internet connections for users in a specific building. The logs show occasional 'DHCP lease renewal failures'. Debug this issue, identify potential root causes, and propose a fix.
A strong answer shows: Systematic debugging methodology; Understanding of network protocols (DHCP, IP); Ability to correlate different data sources.
Design a system to efficiently track and report the number of active mobile users within specific geographic regions (e.g., cities, neighborhoods) in real-time. Assume data streams from millions of devices.
A strong answer shows: Knowledge of spatial data structures; Understanding of real-time data processing; Scalability considerations.
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