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Infotel Conseil Software Engineer Interview Guide

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

The 60-second brief

At Infotel Conseil, a Software Engineer is a key player in delivering high-value digital transformation projects for major clients. You are not just writing code; you are solving complex business challenges by designing, developing, and maintaining robust software solutions that directly impact the operational efficiency of our partners. Your work spans the entire development lifecycle, requiring a blend of technical precision, analytical rigor, and the ability to translate client needs into scalable architecture. This role is highly collaborative and strategically significant. You will often find yourself working within multi-disciplinary teams—engaging with business analysts, project managers, and clients—to ensure that technical deliverables align with organizational objectives.

This guide is scoped to a Software Engineer candidate at Infotel Conseil.

Focus areas

  • Java
  • Spring (framework)
  • Communication technique (explication de projets)

The Infotel Conseil interview process

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

Initial Contact

Brief initial contact to discuss the opportunity and gauge interest.

What to demonstrate

  • Brief initial contact to discuss the opportunity and gauge interest
  • Depth in Java

How to prepare

  • Answer aloud and timed: Can you walk me through a key project you have worked on, focusing on the technologies used and the challenges you overcame?
  • Answer aloud and timed: How would you explain Spring Annotations and their utility in a modern application?

Technical Assessment

Series of technical assessments to evaluate your skills.

What to demonstrate

  • Series of technical assessments to evaluate your skills
  • Depth in Java

How to prepare

  • Answer aloud and timed: What are the fundamental differences between interface implementation and class inheritance in your preferred language?
  • Answer aloud and timed: Can you describe a scenario where you had to perform complex SQL queries to solve a performance bottleneck?

Behavioral Assessment

Behavioral assessments to understand your fit within the company culture.

What to demonstrate

  • Behavioral assessments to understand your fit within the company culture
  • Depth in Java

How to prepare

  • Prepare three examples from your own work, each with a decision you made and an outcome you can quantify.
  • Re-read the description of the behavioral assessment above and write down what you would ask to confirm before it.

Stakeholder Meetings

Meet various stakeholders, including recruiters, business managers, and technical leads.

What to demonstrate

  • Meet various stakeholders
  • Including recruiters, business managers, and technical leads

How to prepare

  • Answer aloud and timed: Can you describe a time you had to deal with a technical disagreement within your team?
  • Answer aloud and timed: What are your primary professional strengths and areas where you are currently seeking improvement?

Where candidates lose points

Own your project history

Be prepared to discuss your role in every project on your CV in detail; interviewers will probe your specific contributions.

Understand the business context

Research the sectors Infotel Conseil operates in to better understand the challenges our clients face.

Be transparent

If you do not know an answer, it is better to admit it and explain how you would find the solution rather than guessing.

Prepare your own questions

Use the time with managers to ask about the team structure, daily workflows, and the types of missions you might be assigned.

Questions & practice

How do you approach a task when the requirements provided by a client are ambiguous?

Medium · Problem-Solving and Case Studies

Approach

  1. Restate the input: its shape, its size, and what is guaranteed about it.
  2. Name the brute-force solution and its complexity before improving on it.
  3. Choose the data structure from the access pattern, not from familiarity.
  4. State the target complexity and say which constraint rules the naive version out.

Follow-up

  • How does this change if the input no longer fits in memory?
  • What is the worst case, and how likely is it on real data?

Merge partitioned event streams into one ordered feed with bounded lateness

Hard · k-way merge · watermarks · out-of-order streams

The read-model service consumes 64 log partitions carrying about 4,000 events per second in total. Each partition is ordered within itself, but partitions drift by up to 30 seconds, and the activity feed must present a tenant's events in occurred_at order. Produce the merge. State its complexity, the buffer it requires in events and in bytes, what happens when one partition is idle, and what you do with an event that arrives after you have already emitted its position. Payloads average 1 KB.

Approach

  1. Merge with a min-heap over the 64 partition heads keyed on (occurred_at, event_id): O(log P) per event and O(n log P) overall. The tie-break on event_id is what makes the output deterministic when two partitions carry the same millisecond, which matters because the feed is paginated and a non-deterministic order reorders pages under the reader.
  2. Emitting the heap head is only correct once every partition has produced everything up to that timestamp, so the emit condition is a watermark: the minimum across partitions of the highest occurred_at seen, less the allowed lateness. Events are held until the watermark passes them, which is what turns individually ordered streams into a jointly ordered one.
  3. Size the buffer from the lateness rather than guessing: 4,000 events per second times 30 seconds is 120,000 buffered events, and at 1 KB each about 120 MB of heap. That number is the real price of the ordering guarantee and belongs in front of whoever asked for it.
  4. Handle the idle partition explicitly, because it fails the feed rather than corrupting it: a partition with no traffic never advances its own maximum, so the watermark freezes and output stops entirely. Either every partition emits a periodic idle marker carrying the broker's current time, or the watermark falls back to wall clock for a partition silent beyond a threshold.

Follow-up

  • The lateness budget is raised to five minutes. What is the new buffer, and what besides memory changes?
  • The consumer restarts. Where does it resume from, and what does the feed look like for the first 30 seconds?

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

  1. 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.
  2. 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.
  3. 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.
  4. 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?

Can you describe a scenario where you had to perform complex SQL queries to solve a performance bottleneck?

Medium · Technical and Domain Expertise

Approach

  1. Name the grain you start from and join outward from it.
  2. Check whether any join is one-to-many before aggregating, or the sums inflate.
  3. Say which index the query would use, and what makes it unusable.
  4. 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?

Find version gaps and relay lag with window functions

Medium · window functions · event tables · frame semantics

outbox_event holds event_id, aggregate_type, aggregate_id, aggregate_version, event_type, payload, status ('pending','published','dead'), attempts, created_at, published_at. A projection is missing rows and you must decide whether the relay skipped events or the consumer dropped them. Write three queries over the last seven days: one listing every aggregate_id whose published aggregate_version sequence has a hole, one giving per-day counts with a running total, and one returning the newest published event per aggregate. For each, say where the window function is evaluated relative to WHERE and LIMIT. PostgreSQL 16.

Approach

  1. Gaps: compute lead(aggregate_version) OVER (PARTITION BY aggregate_id ORDER BY aggregate_version) in a subquery, then filter next_version <> aggregate_version + 1 in the outer query. Window functions are evaluated after WHERE, GROUP BY and HAVING and before the outer ORDER BY and LIMIT, so the predicate cannot sit in the same WHERE clause and PostgreSQL 16 has no QUALIFY.
  2. Say what the seven-day filter does to the answer: it truncates every partition, so the first row per aggregate has no predecessor inside the window and a hole spanning the boundary is invisible. Widen the window, or join to resource.version as the authority for the true maximum.
  3. Running total: SELECT date_trunc('day', created_at) AS d, count() AS n, sum(count()) OVER (ORDER BY date_trunc('day', created_at) ROWS UNBOUNDED PRECEDING). An aggregate inside a window call is legal because grouping runs before windowing. The grouping key is unique per row here so ROWS and RANGE agree, but write the frame anyway — over ungrouped rows with tied timestamps the default RANGE frame pulls in every peer row and the total jumps.
  4. Newest per aggregate: DISTINCT ON (aggregate_id) ... ORDER BY aggregate_id, aggregate_version DESC is the cheap PostgreSQL-only form when an index matches that order; row_number() OVER (PARTITION BY aggregate_id ORDER BY aggregate_version DESC) = 1 is the portable form and needs a subquery for the same evaluation-order reason as the gap query.

Follow-up

  • Relay failover redelivers events. Does a duplicate break the gap query, and how would you detect one from this table alone?
  • Turn the gap check into a continuous monitor rather than a query someone runs after an incident. What does it watch?

Can you walk me through a key project you have worked on, focusing on the technologies used and the challenges

Medium · Technical and Domain Expertise

Can you walk me through a key project you have worked on, focusing on the technologies used and the challenges you overcame?

Approach

  1. Clarify what is being asked and what a complete answer contains.
  2. State your assumptions explicitly before working the problem.
  3. Say what you would check first and why it is the highest-information step.
  4. 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 would you explain Spring Annotations and their utility in a modern application?

Medium · Technical and Domain Expertise

Approach

  1. Clarify what is being asked and what a complete answer contains.
  2. State your assumptions explicitly before working the problem.
  3. Say what you would check first and why it is the highest-information step.
  4. 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 the fundamental differences between interface implementation and class inheritance in your preferred

Medium · Technical and Domain Expertise

What are the fundamental differences between interface implementation and class inheritance in your preferred language?

Approach

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

Follow-up

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

If a production system you are responsible for experiences a sudden performance drop, what is your systematic

Medium · Problem-Solving and Case Studies

If a production system you are responsible for experiences a sudden performance drop, what is your systematic approach to debugging?

Approach

  1. Establish what changed and when, before forming any theory.
  2. Pick a bisection that eliminates candidates whichever way it turns out.
  3. Check the instrumentation before believing the symptom.
  4. Separate the trigger from the cause; the deploy is rarely the bug.

Follow-up

  • What would you look at first, and what would it rule out?
  • How would you tell a cause from a coincidence here?

Suggested practice checklist

Built from the rounds and topics Infotel Conseil candidates report.

Day 1 — Map the Infotel Conseil loop

  • Write out the reported sequence: Initial Contact, Technical Assessment, Behavioral Assessment, Stakeholder Meetings.
  • 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 Java

  • Spend the session on Java, which Infotel Conseil candidates report being tested on.
  • Write one worked example in Java and time yourself on it.

Deliverable: One timed worked example in Java.

Day 3 — Work Spring (framework)

  • Spend the session on Spring (framework), which Infotel Conseil candidates report being tested on.
  • Write one worked example in Spring (framework) and time yourself on it.

Deliverable: One timed worked example in Spring (framework).

Day 4 — Work Communication technique (explication de projets)

  • Spend the session on Communication technique (explication de projets), which Infotel Conseil candidates report being tested on.
  • Write one worked example in Communication technique (explication de projets) and time yourself on it.

Deliverable: One timed worked example in Communication technique (explication de projets).

Day 5 — Answer out loud: Technical and Domain Expertise

  • Answer aloud, timed: Can you walk me through a key project you have worked on, focusing on the technologies used and the challenges you overcame?
  • Answer aloud, timed: How would you explain Spring Annotations and their utility in a modern application?

Deliverable: Spoken answers to 2 reported Technical and Domain Expertise question(s), under time.

Day 6 — Answer out loud: Behavioral and Professional Alignment

  • Answer aloud, timed: Tell me about yourself and how your career path has led you to apply for this Software Engineer position.
  • Answer aloud, timed: Can you describe a time you had to deal with a technical disagreement within your team?

Deliverable: Spoken answers to 2 reported Behavioral and Professional Alignment question(s), under time.

Day 7 — Answer out loud: Problem-Solving and Case Studies

  • Answer aloud, timed: How do you approach a task when the requirements provided by a client are ambiguous?
  • Answer aloud, timed: If a production system you are responsible for experiences a sudden performance drop, what is your systematic approach to debugging?

Deliverable: Spoken answers to 2 reported Problem-Solving and Case Studies question(s), under time.

Behavioural preparation

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

How do you handle method overloading versus method overriding in your code?

Medium · Technical and Domain Expertise

Approach

  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. 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?

Tell me about yourself and how your career path has led you to apply for this Software Engineer position.

Medium · Behavioral and Professional Alignment

Approach

  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. 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?

Can you describe a time you had to deal with a technical disagreement within your team?

Medium · Behavioral and Professional Alignment

Approach

  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. 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 primary professional strengths and areas where you are currently seeking improvement?

Medium · Behavioral and Professional Alignment

Approach

  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. 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?

Why are you interested in joining Infotel Conseil specifically?

Medium · Behavioral and Professional Alignment

Approach

  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. 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?