Interview guides · Inetum

Inetum Software Engineer Interview Guide

Inetum Software Engineer interview guide: reported rounds, questions and how candidates describe the process.

The 60-second brief

A Software Engineer at Inetum plays a pivotal role in driving digital flow for thousands of clients worldwide. As an international IT services and consulting company (formerly known as Gfi Informatique), Inetum positions its engineers at the intersection of cutting-edge technology and strategic business consulting. In this role, you will not simply write code in isolation; you will design, build, and modernize critical software systems that solve complex, real-world challenges for major enterprises across banking, public administration, automotive, and telecommunications. The impact of a Software Engineer at Inetum is highly visible. You will join project teams that help clients transition to modern cloud architectures, implement robust backend systems, or build intuitive frontend interfaces.

This guide is scoped to a Software Engineer candidate at Inetum.

Focus areas

Soft Skills (Communication)
Technical Knowledge Assessment
Backend Development

The Inetum interview process

Inetum candidates report 4 rounds over 3-5 weeks. The stages below are what candidates describe, not a published process.

Initial Screening Call

A conversational interview with a Talent Acquisition Specialist to discuss your background, salary expectations, and career goals.

What to demonstrate

A conversational interview with a Talent Acquisition Specialist to discuss your background, salary expectations, and career goals
Depth in Soft Skills (Communication)

How to prepare

Be able to walk your CV end to end in two minutes, and say why this company specifically.
Have your salary expectations, notice period and location constraints ready, and ask for the rest of the loop in writing.

Technical Evaluation

Includes an online assessment like Codingame followed by a deep-dive technical interview with a Technical Architect or Lead Developer.

What to demonstrate

Includes an online assessment like Codingame followed by a deep-dive technical interview with a Technical Architect or Lead Developer
Depth in Soft Skills (Communication)

How to prepare

Answer aloud and timed: How do you manage dependency injection in Spring Boot or.NET?
Answer aloud and timed: What is the difference between an interface and an abstract class, and when would you use each?

Project-Matching Discussion

Meeting with a Business Unit Manager or Client Partner to discuss specific client projects and contract conditions.

What to demonstrate

Meeting with a Business Unit Manager or Client Partner to discuss specific client projects and contract conditions
Depth in Soft Skills (Communication)

How to prepare

Answer aloud and timed: Explain how RESTful web services handle state and security.
Answer aloud and timed: How do you handle a situation where a client requests a feature that is technically unfeasible within the current architecture?

Final Client Interview

A brief interview with an Inetum client to finalize your placement, depending on the hiring approach.

What to demonstrate

A brief interview with an Inetum client to finalize your placement, depending on the hiring approach
Depth in Soft Skills (Communication)

How to prepare

Answer aloud and timed: Describe a time when you had to manage a high-pressure deadline. How did you organize your work?
Answer aloud and timed: How do you explain complex technical concepts to non-technical stakeholders or business clients?

Where candidates lose points

Be transparent about your career goals

Inetum managers want to know what technologies or industries interest you. This helps them align you with the right client projects and build a sustainable career plan.

Do not overcomplicate your technical answers

When asked technical questions, provide clear, concise, and production-oriented explanations. Avoid overly academic jargon unless it directly serves the answer.

Clarify contract and project details early

Ask questions about the duration of the potential mission, the location of the client, and the expectations regarding hybrid work to ensure there are no surprises later.

Research Inetum’s local presence

Inetum operates globally but has strong regional roots. Familiarize yourself with major client sectors in your specific location (e.g., public sector in France, banking in Spain) to show local market awareness.

Questions & practice

Find overlapping job attempts and peak concurrency from lease records

Medium · sweep line · intervals · leases

A day of job_run history yields about 50,000,000 attempt records: (job_run_id, job_type, attempt, started_at, finished_at which is NULL when the worker died, lease_expires_at). Leases expire on a clock, so a job that outran its lease ran twice. Produce (a) every job_run_id whose attempts overlapped in wall-clock time and (b) the peak number of simultaneously running attempts per job_type with the minute it occurred. Target O(n log n). State how you treat a NULL finished_at and what clock skew does to your answer.

Approach

Define the interval before sorting anything: an attempt occupies [started_at, COALESCE(finished_at, lease_expires_at)). finished_at is observed and lease_expires_at is only a promise, so every attempt without a finish contributes an estimate and the whole result is a lower bound on overlap rather than an exact count.
For peak concurrency, sweep: emit 2n endpoints, sort by (timestamp, kind) with ends ordered before starts at equal timestamps, then walk the sequence maintaining a counter per job_type and record each type's maximum with its timestamp. O(n log n) dominated by the sort, O(n) space, or O(1) extra if the sort is external and the walk streams.
For overlap detection, do not compare attempts pairwise. A single global sort by (job_run_id, started_at) gives both the grouping and the order; within a group, keep the maximum end seen so far and report an overlap exactly when the next start is less than that running maximum, which is one linear pass after the sort.
Half-open intervals matter and are easy to get wrong: with closed intervals an attempt ending at the same millisecond another begins reads as concurrency two, and across 50,000,000 records that artefact swamps the real signal.

Follow-up

A handler is not idempotent and you have found 400 overlapping jobs. Which of them actually caused damage, and what would you query to find out?
Peak concurrency for one job_type is 4 against a configured cap of 4. Is the cap working, or is the data hiding attempts that never started?

Canonicalise a request body into a stable idempotency fingerprint

Medium · parsing · canonicalisation · hashing

idempotency_key.request_fingerprint is a SHA-256 over the method, path and canonicalised body, and a retry whose fingerprint differs must be rejected with 422 rather than served the stored response. Write the canonicaliser. Bodies are JSON up to 256 KB nested at most 32 levels; clients vary key order, whitespace and unicode escaping, and some send 64-bit ids as JSON numbers. Produce a deterministic byte string such that semantically identical bodies match and any semantic difference does not. State your complexity and name two normalisations you refuse to perform.

Approach

Parse once into a tree, then re-serialise under fixed rules: object keys sorted, array order preserved, one escaping convention, no insignificant whitespace. Parsing is O(n) and sorting keys is O(k log k) per object, so O(n log n) overall with O(depth) stack, and the 32-level cap is enforced during parsing because hostile nesting is how a canonicaliser becomes a stack overflow.
Sort keys by their UTF-8 bytes and say why the obvious implementation is wrong in some runtimes: a default string comparison that orders by UTF-16 code units places surrogate pairs, meaning code points from U+10000 up, below U+E000 to U+FFFF, which is not UTF-8 byte order, so two services written in different languages disagree on the same document.
Do not re-encode numbers through a double. IEEE-754 binary64 represents integers exactly only up to 2^53, so normalising a 19-digit id through a float changes it, and 1 against 1.0 cannot be reconciled without deciding whether they are the same value. Preserve the literal token, and require ids as strings at the API boundary if you want them comparable.
Reject duplicate keys rather than picking one. JSON permits them and parsers disagree, most keeping the last, so any choice you make ties the fingerprint to a parser detail that the code handling the request does not necessarily share.

Follow-up

A client sends the same logical request with an extra field your API ignores. Same key, different fingerprint, so you return 422. Is that the right answer?
Where does the fingerprint get computed relative to request decompression and the body-size limit?

Collapse a redelivered event batch into per-aggregate high-water marks

Easy · hashing · at-least-once · aggregation

You drain a batch of up to 5,000,000 events, each (aggregate_id BIGINT, aggregate_version INT, event_type, payload). The log guarantees order within one aggregate only; the batch merges 64 partitions, and a relay failover has redelivered a range, so an older version for an aggregate can appear after a newer one. Given a map of last_applied_version per aggregate, produce the events worth applying, at most one per (aggregate_id, version), plus the count discarded. Target O(n) time. State the memory for 2,000,000 distinct aggregates and what you do when it does not fit.

Approach

One pass, one hash map from aggregate_id to the highest version kept, and a discard counter. An event whose version is at or below last_applied_version for its aggregate is dropped without further work, which is the whole reason the event carries its version rather than a delta. O(n) expected time, O(d) space in distinct aggregates.
Keep the maximum, never the last occurrence. The redelivered range means the final appearance of an aggregate in the batch can be an older version than one seen earlier in the same batch, so last-wins applies stale state over newer state and the projection regresses with no error anywhere.
Cost the memory instead of calling it large: an 8-byte key plus a 4-byte version is 12 bytes of payload, and an open-addressed table held at a 0.7 load factor costs roughly 17 bytes per entry before per-slot metadata, so 2,000,000 aggregates is tens of megabytes in a native layout and several times that in a runtime that boxes both key and value.
If the distinct set exceeds memory, partition on hash(aggregate_id) mod P and reduce each partition independently. Every event for one aggregate hashes to the same partition, so the per-partition result is exact and the merge is concatenation rather than a second reduction.

Follow-up

The payload is a patch rather than a snapshot, so applying only the highest version loses the intermediate changes. What changes in your reduction?
How do you detect that version 7 arrived while version 6 was never delivered, and what should the consumer do about the gap?

What are the main differences between a relational database like SQL Server and a NoSQL database?

Medium · Technical & Core Programming

Approach

Name the grain you start from and join outward from it.
Check whether any join is one-to-many before aggregating, or the sums inflate.
Say which index the query would use, and what makes it unusable.
Handle the rows that do not match: that is usually the actual question.

Follow-up

How does the query change if that join becomes one-to-many?
What happens to this when the table is ten times larger?

Denormalise tenant onto revisions and backfill it live

Hard · denormalisation · online migration · backfill

resource_revision (revision_id, resource_id, version, actor_user_id, change_kind, patch, request_id, created_at) has 400M rows and no tenant column; tenant_id lives only on resource. Two reads need it: a tenant-scoped audit feed ordered by created_at DESC, and an offboarding purge. Both join back to resource today. Justify adding tenant_id to resource_revision against those two reads, name the anomaly the copy introduces and the constraint that prevents it, then give the ordered migration for a live table taking 1.2k writes/second — the lock each step takes, how the backfill is batched, and where each step stops being reversible. PostgreSQL 16.

Approach

Justify from the access path rather than from taste. Without the column, the audit feed either scans resource_revision by created_at and discards other tenants' rows, or resolves the tenant's resource_ids first and probes with them — both proportional to the tenant's whole history rather than to one page. With (tenant_id, created_at DESC, revision_id DESC) it is a seek that stops at 50 rows, and the purge becomes a ranged delete instead of a join.
Name the cost exactly: a second copy of a fact can disagree with the first. Make the disagreement unwritable rather than documented — add UNIQUE (resource_id, tenant_id) on resource so it can serve as a foreign-key target, then FOREIGN KEY (resource_id, tenant_id) REFERENCES resource (resource_id, tenant_id) on the revision table. A revision can then only ever carry its parent's tenant.
Step one, expand: ALTER TABLE resource_revision ADD COLUMN tenant_id BIGINT NULL, with no default, so it is a catalogue change and no rewrite. It still needs ACCESS EXCLUSIVE for an instant, and that instant queues behind the longest open transaction on the table while every later query queues behind it — set lock_timeout to 2s and retry rather than wait.
Step two, dual-write: deploy the writer that populates tenant_id on every new revision while reads still use the join. Reversible by redeploying the previous build, because nothing reads the column yet.

Follow-up

The backfill is half finished and a rollback is required. What state is the table in, and what does the previous build do with a half-populated column?
How do you verify the backfill actually finished, given rows are still being inserted while it runs?

Explain the concept of polymorphism in object-oriented programming and provide a real-world example.

Medium · Technical & Core Programming

Approach

Clarify what is being asked and what a complete answer contains.
State your assumptions explicitly before working the problem.
Say what you would check first and why it is the highest-information step.
Work from the requirement backwards to the design.

Follow-up

What assumption would you test first?
How would you know your answer was wrong?

How do you manage dependency injection in Spring Boot or.NET?

Medium · Technical & Core Programming

Approach

Clarify what is being asked and what a complete answer contains.
State your assumptions explicitly before working the problem.
Say what you would check first and why it is the highest-information step.
Work from the requirement backwards to the design.

Follow-up

What assumption would you test first?
How would you know your answer was wrong?

What is the difference between an interface and an abstract class, and when would you use each?

Medium · Technical & Core Programming

Approach

Clarify what is being asked and what a complete answer contains.
State your assumptions explicitly before working the problem.
Say what you would check first and why it is the highest-information step.
Work from the requirement backwards to the design.

Follow-up

What assumption would you test first?
How would you know your answer was wrong?

Explain how RESTful web services handle state and security.

Medium · Technical & Core Programming

Approach

Clarify what is being asked and what a complete answer contains.
State your assumptions explicitly before working the problem.
Say what you would check first and why it is the highest-information step.
Work from the requirement backwards to the design.

Follow-up

What assumption would you test first?
How would you know your answer was wrong?

Walk me through your resume and highlight the project you are most proud of.

Medium · Experience & Motivation

Approach

Clarify what is being asked and what a complete answer contains.
State your assumptions explicitly before working the problem.
Say what you would check first and why it is the highest-information step.
Work from the requirement backwards to the design.

Follow-up

What assumption would you test first?
How would you know your answer was wrong?

Why are you interested in working for an IT consulting company like Inetum rather than a traditional product c

Medium · Experience & Motivation

Why are you interested in working for an IT consulting company like Inetum rather than a traditional product company?

Approach

Clarify what is being asked and what a complete answer contains.
State your assumptions explicitly before working the problem.
Say what you would check first and why it is the highest-information step.
Work from the requirement backwards to the design.

Follow-up

What assumption would you test first?
How would you know your answer was wrong?

What are your expectations regarding remote work, hybrid settings, and traveling to client sites?

Medium · Experience & Motivation

Approach

Clarify what is being asked and what a complete answer contains.
State your assumptions explicitly before working the problem.
Say what you would check first and why it is the highest-information step.
Work from the requirement backwards to the design.

Follow-up

What assumption would you test first?
How would you know your answer was wrong?

How do you keep your technical skills up to date with rapidly changing technologies?

Medium · Experience & Motivation

Approach

Clarify what is being asked and what a complete answer contains.
State your assumptions explicitly before working the problem.
Say what you would check first and why it is the highest-information step.
Work from the requirement backwards to the design.

Follow-up

What assumption would you test first?
How would you know your answer was wrong?

What specific technologies or domains are you looking to specialize in next?

Medium · Experience & Motivation

Approach

Clarify what is being asked and what a complete answer contains.
State your assumptions explicitly before working the problem.
Say what you would check first and why it is the highest-information step.
Work from the requirement backwards to the design.

Follow-up

What assumption would you test first?
How would you know your answer was wrong?

Every query on one table stalls for forty seconds mid-deploy

Medium · lock contention · ddl · migrations

During a release on PostgreSQL, every query touching resource times out for about 40 seconds and then recovers with no intervention. The release ran one migration, ALTER TABLE resource ADD COLUMN archived_reason TEXT, and the migration log shows it completing in 6 ms. Unrelated tables showed no change in error rate. Explain how a 6 ms statement caused a 40-second stall, give the ordered checks you would run on a live system to confirm it, and give the migration procedure that prevents a repeat.

Approach

Separate the statement's duration from the lock's duration. ADD COLUMN with no default is a catalogue-only change and genuinely runs in milliseconds, but it requires ACCESS EXCLUSIVE, and it cannot acquire that until every transaction already touching the table has finished.
Account for the queueing, which is the part that surprises people. A lock request that is waiting blocks later requests for conflicting modes behind it rather than letting them overtake, so one long-open transaction holds the DDL and the DDL holds all the traffic. The stall length is set by the longest open transaction, not by the size of the change.
Confirm on a live system in this order: pg_stat_activity for that table ordered by xact_start, looking for the oldest transaction and specifically for state = idle in transaction; then pg_locks where granted = false to find the waiter; then join them on pid to name blocker and blocked. pg_blocking_pids() does that join for you and is the fastest single call.
Prevent rather than merely time it better. Set lock_timeout to a second or two on the migration session so the DDL abandons the queue after a bounded wait and is retried, instead of holding it for as long as the oldest transaction lives. Be exact about what that buys: queries arriving during the wait still queue behind the pending ACCESS EXCLUSIVE request, so each attempt costs them up to one lock_timeout of added latency. The outage goes from 40 seconds to about one second per attempt, not to zero. Also run migrations away from deploy-time peaks, and put a statement timeout and an idle-in-transaction timeout on the analytics role that opens the long transactions.

Follow-up

The same release also wants NOT NULL on that column. What is the sequence that gets there without a long lock?
Your lock_timeout retry fails ten times in a row because the analytics transaction is always open. What do you change?

Suggested practice checklist

Built from the rounds and topics Inetum candidates report.

Day 1 — Map the Inetum loop

Write out the reported sequence: Initial Screening Call, Technical Evaluation, Project-Matching Discussion, Final Client Interview.
For each round, write one sentence on what it is judging, from the description above, and mark the one you are least ready for.

Deliverable: A one-page map of the 4 reported rounds, with the weakest marked.

Day 2 — Work Soft Skills (Communication)

Spend the session on Soft Skills (Communication), which Inetum candidates report being tested on.
Write one worked example in Soft Skills (Communication) and time yourself on it.

Deliverable: One timed worked example in Soft Skills (Communication).

Day 3 — Work Technical Knowledge Assessment

Spend the session on Technical Knowledge Assessment, which Inetum candidates report being tested on.
Write one worked example in Technical Knowledge Assessment and time yourself on it.

Deliverable: One timed worked example in Technical Knowledge Assessment.

Day 4 — Work Backend Development

Spend the session on Backend Development, which Inetum candidates report being tested on.
Write one worked example in Backend Development and time yourself on it.

Deliverable: One timed worked example in Backend Development.

Day 5 — Answer out loud: Technical & Core Programming

Answer aloud, timed: Explain the concept of polymorphism in object-oriented programming and provide a real-world example.
Answer aloud, timed: What are the main differences between a relational database like SQL Server and a NoSQL database?

Deliverable: Spoken answers to 2 reported Technical & Core Programming question(s), under time.

Day 6 — Answer out loud: Behavioral & Client Interaction

Answer aloud, timed: How do you handle a situation where a client requests a feature that is technically unfeasible within the current architecture?
Answer aloud, timed: Describe a time when you had to manage a high-pressure deadline. How did you organize your work?

Deliverable: Spoken answers to 2 reported Behavioral & Client Interaction question(s), under time.

Day 7 — Answer out loud: Experience & Motivation

Answer aloud, timed: Walk me through your resume and highlight the project you are most proud of.
Answer aloud, timed: Why are you interested in working for an IT consulting company like Inetum rather than a traditional product company?

Deliverable: Spoken answers to 2 reported Experience & Motivation question(s), under time.

Behavioural preparation

Behavioural rounds judge the decision you made and what it cost.

How do you handle a situation where a client requests a feature that is technically unfeasible within the curr

Medium · Behavioral & Client Interaction

How do you handle a situation where a client requests a feature that is technically unfeasible within the current architecture?

Approach

Pick a story where you made the decision, not one where you watched it.
State the situation in two sentences and spend the rest on the reasoning.
Give the blast radius: what could have broken, and what you measured.
Name the disagreement and how you resolved it with evidence.

Follow-up

What would you do differently if you ran that again?
How did you know your change caused the improvement?

Describe a time when you had to manage a high-pressure deadline. How did you organize your work?

Medium · Behavioral & Client Interaction

Approach

Pick a story where you made the decision, not one where you watched it.
State the situation in two sentences and spend the rest on the reasoning.
Give the blast radius: what could have broken, and what you measured.
Name the disagreement and how you resolved it with evidence.

Follow-up

What would you do differently if you ran that again?
How did you know your change caused the improvement?

How do you explain complex technical concepts to non-technical stakeholders or business clients?

Medium · Behavioral & Client Interaction

Approach

Pick a story where you made the decision, not one where you watched it.
State the situation in two sentences and spend the rest on the reasoning.
Give the blast radius: what could have broken, and what you measured.
Name the disagreement and how you resolved it with evidence.

Follow-up

What would you do differently if you ran that again?
How did you know your change caused the improvement?

What are your career objectives for the next three years, and how does consulting fit into them?

Medium · Behavioral & Client Interaction

Approach

Pick a story where you made the decision, not one where you watched it.
State the situation in two sentences and spend the rest on the reasoning.
Give the blast radius: what could have broken, and what you measured.
Name the disagreement and how you resolved it with evidence.

Follow-up

What would you do differently if you ran that again?
How did you know your change caused the improvement?

Describe a situation where you had to work with a difficult team member. How did you resolve the conflict?

Medium · Behavioral & Client Interaction

Approach

Pick a story where you made the decision, not one where you watched it.
State the situation in two sentences and spend the rest on the reasoning.
Give the blast radius: what could have broken, and what you measured.
Name the disagreement and how you resolved it with evidence.

Follow-up

What would you do differently if you ran that again?
How did you know your change caused the improvement?