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Gallup Software Engineer Interview Guide

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

The 60-second brief

A Software Engineer at Gallup plays a pivotal role in developing innovative solutions that drive data-driven insights and enhance user experiences. Your contributions will directly impact products that empower organizations and individuals to make informed decisions based on their unique strengths and data analytics. You will work on a range of projects, from backend systems that handle complex data processing to frontend applications that deliver intuitive user interfaces. Given Gallup's commitment to leveraging technology for meaningful results, you will find yourself at the intersection of engineering and user-centric design. The work is not only technically challenging but also deeply rewarding, as you will be part of a team that influences the direction of the company’s offerings in survey methodology, analytics, and organizational performance.

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

Focus areas

  • Behavioral Interviewing (Competency-based)
  • Online Behavioral Assessment
  • Team Management Skills

The Gallup interview process

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

Online Assessment

Candidates complete an online behavioral assessment to evaluate fit for the role and organization.

What to demonstrate

  • Candidates complete an online behavioral assessment to evaluate fit for the role and organization
  • Depth in Behavioral Interviewing (Competency-based)

How to prepare

  • Answer aloud and timed: Describe a time you faced a significant challenge at work. How did you handle it?
  • Answer aloud and timed: Can you give an example of when you had to work with a difficult team member?

Phone Interviews

Successful candidates participate in phone interviews with HR and technical leads, focusing on general and technical questions.

What to demonstrate

  • Successful candidates participate in phone interviews with HR and technical leads
  • Focusing on general and technical questions

How to prepare

  • Answer aloud and timed: How do you prioritize your tasks when faced with multiple deadlines?
  • Answer aloud and timed: Tell me about a time you took a risk and what the outcome was.

In-Person Interview

Candidates who perform well may be invited to an in-person interview or a technical assessment tailored to their skills.

What to demonstrate

  • Candidates who perform well may be invited to an in-person interview or a technical assessment tailored to their skills
  • Depth in Behavioral Interviewing (Competency-based)

How to prepare

  • Answer aloud and timed: Describe a situation where you had to persuade others to adopt your point of view.
  • Answer aloud and timed: What programming languages are you most comfortable with, and why?

Where candidates lose points

Prepare for Behavioral Questions

Practice articulating your experiences with the STAR method (Situation, Task, Action, Result) to provide structured responses.

Research the Company

Familiarize yourself with Gallup’s mission, values, and recent projects to demonstrate your interest and alignment during interviews.

Showcase Your Projects

Be ready to discuss significant projects you’ve worked on, including the challenges faced and the outcomes achieved.

Ask Insightful Questions

Prepare thoughtful questions to ask your interviewers about the team culture, projects, and opportunities for growth within the company.

Questions & practice

Write a function to reverse a linked list.

Medium · Coding / Algorithms (if applicable)

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?

How would you implement a binary search algorithm?

Medium · Coding / Algorithms (if applicable)

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?

Track a rolling failure rate per destination for circuit decisions

Easy · sliding window · ring buffer · circuit breaker

The egress service delivers about 1,500 webhooks per second across roughly 40,000 destinations, each call bounded by a 10 second timeout. Maintain, per destination, the failure rate over the trailing 60 seconds so a caller can ask before dispatch whether the circuit should open. Attempts arrive as (destination_id, finished_at_ms, outcome). Requirement: amortised O(1) per attempt, with total memory bounded by the destination count rather than by traffic. Give the structure, its exact memory, and the rule that stops a destination with three attempts from opening a circuit.

Approach

  1. Name the exact-deque version and then reject it as the default. Holding timestamps and advancing a tail pointer past anything older than now minus 60 seconds is a correct two-pointer window at amortised O(1) per attempt, but its memory tracks in-window traffic, so one destination in a retry storm holds hundreds of thousands of entries while thousands of quiet destinations hold none.
  2. Use a ring of 60 one-second buckets per destination, each bucket a pair of counters for attempts and failures. On an attempt, advance the ring by the elapsed whole seconds, zeroing at most min(elapsed, 60) buckets, then increment the head. That is amortised O(1) with a fixed footprint per destination.
  3. State the footprint: 60 buckets times two 4-byte counters is 480 bytes of payload per destination, so 40,000 destinations is roughly 20 to 25 MB with per-entry overhead, bounded by the catalogue rather than by the rate. The cost is granularity, since the oldest bucket ages out in whole seconds, which is far tighter than the decision needs.
  4. Require a minimum sample before the circuit may open. A destination with three attempts and three failures reads as 100 percent and is not evidence; a floor of roughly 20 attempts in the window makes the ratio meaningful, and below that floor use a run of consecutive failures as the trigger instead.

Follow-up

  • The fleet is 30 instances and each sees roughly a thirtieth of a destination's traffic. Where does the rate actually live, and what does a per-instance answer get wrong?
  • A destination answers in 9.5 seconds and succeeds. It is not failing but it is consuming your per-destination concurrency. What signal should open the circuit here?

Explain how you would optimize a slow-running query in a database.

Medium · Coding / Algorithms (if applicable)

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?

Hold a per-tenant active cap against concurrent creates

Hard · write skew · isolation levels · constraints

A tenant on the standard plan may hold at most 50 resources with status='active'. The create handler runs SELECT count(*) FROM resource WHERE tenant_id = $1 AND status = 'active', compares to 50, then inserts. Two creates arrive 3 ms apart on different instances and the tenant lands at 51. Name the anomaly, say whether PostgreSQL 16 READ COMMITTED or REPEATABLE READ prevents it and why, then give an implementation that holds the cap at READ COMMITTED with the exact statements. Finally, say what changes when the cap is 'at most one running export per tenant' on job_run.

Approach

  1. Name it: write skew. The two transactions read an overlapping set and write disjoint rows, so there is no row-level conflict for the engine to detect and each commit is individually legal.
  2. Rule out the levels precisely. READ COMMITTED takes a fresh snapshot per statement and takes no lock on the counted rows, so both see 49. PostgreSQL's REPEATABLE READ is snapshot isolation: it removes non-repeatable reads and phantoms within the snapshot but still admits write skew, because the anomaly is not a re-read of a changed row, it is a read of a set that a concurrent transaction invalidates. Only SERIALIZABLE closes it, by tracking the read dependency and aborting one transaction with SQLSTATE 40001 — a guarantee that exists only if the application re-runs the whole transaction from the read.
  3. Convert the set predicate into a single-row conflict: keep tenant.active_resource_count and run UPDATE tenant SET active_resource_count = active_resource_count + 1 WHERE tenant_id = $1 AND active_resource_count < 50 in the same transaction as the INSERT. Zero affected rows is the cap, returned as 409. The row lock serialises the decision at any isolation level, and contention is bounded to one tenant's row — which is also the fair-scheduling unit, unlike a global counter that would convoy every tenant behind one row.
  4. State the cost you just took on: a counter is a second source of truth that can drift, so every path that changes status must adjust it inside the same transaction, and a periodic reconciliation has to exist, with resource_revision as the authority for what the count should have been.

Follow-up

  • A resource moves from archived back to active. Which statements change, and what breaks if the counter update and the status change land in different transactions?
  • The cap becomes plan-dependent and a plan can change mid-month. Where does the number 50 live, and who reads it?

What programming languages are you most comfortable with, and why?

Medium · Technical / Domain Questions

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?

Explain the differences between object-oriented and functional programming.

Medium · Technical / Domain Questions

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?

Describe a project where you implemented a significant technical solution.

Medium · Technical / Domain Questions

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 do you ensure code quality and maintainability?

Medium · Technical / Domain Questions

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 project is behind schedule, what steps would you take to get it back on track?

Medium · Problem-Solving / Case Studies

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?

Describe a scenario where you had to analyze data to make a decision.

Medium · Problem-Solving / Case Studies

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 prioritize features for a new software release?

Medium · Problem-Solving / Case Studies

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 approach debugging a complex issue in production?

Medium · Problem-Solving / Case Studies

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 Gallup candidates report.

Day 1 — Map the Gallup loop

  • Write out the reported sequence: Online Assessment, Phone Interviews, In-Person 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 3 reported rounds, with the weakest marked.

Day 2 — Work Behavioral Interviewing (Competency-based)

  • Spend the session on Behavioral Interviewing (Competency-based), which Gallup candidates report being tested on.
  • Write one worked example in Behavioral Interviewing (Competency-based) and time yourself on it.

Deliverable: One timed worked example in Behavioral Interviewing (Competency-based).

Day 3 — Work Online Behavioral Assessment

  • Spend the session on Online Behavioral Assessment, which Gallup candidates report being tested on.
  • Write one worked example in Online Behavioral Assessment and time yourself on it.

Deliverable: One timed worked example in Online Behavioral Assessment.

Day 4 — Work Team Management Skills

  • Spend the session on Team Management Skills, which Gallup candidates report being tested on.
  • Write one worked example in Team Management Skills and time yourself on it.

Deliverable: One timed worked example in Team Management Skills.

Day 5 — Answer out loud: Behavioral / Leadership Questions

  • Answer aloud, timed: Describe a time you faced a significant challenge at work. How did you handle it?
  • Answer aloud, timed: Can you give an example of when you had to work with a difficult team member?

Deliverable: Spoken answers to 2 reported Behavioral / Leadership Questions question(s), under time.

Day 6 — Answer out loud: Technical / Domain Questions

  • Answer aloud, timed: What programming languages are you most comfortable with, and why?
  • Answer aloud, timed: Explain the differences between object-oriented and functional programming.

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

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

  • Answer aloud, timed: How would you approach debugging a complex issue in production?
  • Answer aloud, timed: If a project is behind schedule, what steps would you take to get it back on track?

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

Behavioural preparation

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

Describe a time you faced a significant challenge at work. How did you handle it?

Medium · Behavioral / Leadership Questions

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 give an example of when you had to work with a difficult team member?

Medium · Behavioral / Leadership Questions

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?

How do you prioritize your tasks when faced with multiple deadlines?

Medium · Behavioral / Leadership Questions

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 a time you took a risk and what the outcome was.

Medium · Behavioral / Leadership Questions

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?

Describe a situation where you had to persuade others to adopt your point of view.

Medium · Behavioral / Leadership Questions

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 walk us through your experience with databases and SQL?

Medium · Technical / Domain Questions

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 do you think is the most important value in a team environment?

Medium · Culture Fit / Values

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?

How do you handle feedback, both giving and receiving?

Medium · Culture Fit / Values

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 do you want to work at Gallup?

Medium · Culture Fit / Values

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 does it mean to you to work in a strengths-based environment?

Medium · Culture Fit / Values

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?