Interview guides · First Horizon

First Horizon Software Engineer Interview Guide

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

The 60-second brief

As a Software Engineer at First Horizon, you serve as a pivotal contributor to the technological infrastructure that powers one of the region’s most prominent financial institutions. Your work directly impacts the stability, security, and efficiency of systems that support both internal operations and client-facing financial services. Whether you are working on client platform support, system integration, or core banking applications, your role is to ensure that technology remains a seamless enabler of the business. This position is critical because it bridges the gap between complex banking requirements and reliable software solutions. You will be expected to balance technical precision with a deep understanding of the regulatory and operational needs of a financial environment.

This guide is scoped to a Software Engineer candidate at First Horizon.

Focus areas

Software Engineering (general)
Technical Interviewing (problem-solving tasks)
Coding Exercises / Code Tests

The First Horizon interview process

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

Recruiter Screening

Initial interaction with a recruiter to discuss your background and fit for the role.

What to demonstrate

Initial interaction with a recruiter to discuss your background and fit for the role
Depth in Software Engineering (general)

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 Assessments

Technical interviews or assessments to evaluate your practical experience and skills.

What to demonstrate

Technical interviews or assessments to evaluate your practical experience and skills
Depth in Software Engineering (general)

How to prepare

Answer aloud and timed: How do you approach debugging or troubleshooting a system that is failing in production?
Answer aloud and timed: Describe a time you had to learn a new tool or framework under a tight deadline.

Managerial Discussions

Conversations with managerial staff to assess team fit and further evaluate your capabilities.

What to demonstrate

Conversations with managerial staff to assess team fit and further evaluate your capabilities
Depth in Software Engineering (general)

How to prepare

Answer aloud and timed: How do you ensure your code is maintainable and scalable?
Answer aloud and timed: Describe a time you disagreed with a technical decision made by a team lead. How did you handle it?

Where candidates lose points

Know your resume

Be prepared to speak in detail about any project you have listed. Interviewers will often ask you to elaborate on the challenges you faced and the specific technologies you utilized.

Research the role

Understand the specific requirements of the team you are interviewing for. If the role is in client platform support, emphasize your experience with user-facing systems and troubleshooting.

Be prepared for behavioral questions

Use the STAR method (Situation, Task, Action, Result) to structure your stories. This ensures you provide concise, impactful answers.

Ask thoughtful questions

At the end of your interviews, ask about the team’s current priorities or how they handle technical challenges. This demonstrates your genuine interest and professional maturity.

Questions & practice

Can you walk me through your thought process for solving a common data handling task in your primary language?

Medium · Practical Coding and Problem Solving

Approach

Restate the input: its shape, its size, and what is guaranteed about it.
Name the brute-force solution and its complexity before improving on it.
Choose the data structure from the access pattern, not from familiarity.
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?

Given a specific scenario, how would you optimize an existing script for better performance?

Medium · Practical Coding and Problem Solving

Approach

Restate the input: its shape, its size, and what is guaranteed about it.
Name the brute-force solution and its complexity before improving on it.
Choose the data structure from the access pattern, not from familiarity.
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?

What are the common security considerations you keep in mind when writing code for banking or client-facing pl

Medium · Practical Coding and Problem Solving

What are the common security considerations you keep in mind when writing code for banking or client-facing platforms?

Approach

Restate the input: its shape, its size, and what is guaranteed about it.
Name the brute-force solution and its complexity before improving on it.
Choose the data structure from the access pattern, not from familiarity.
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?

Stop tag and share joins from fanning out a page

Medium · join fan-out · semi-joins · many-to-many

resource_tag is (resource_id, tag_id) with PK (resource_id, tag_id); resource_share is (resource_id, shared_with_user_id, permission). The tagged-and-shared listing inner-joins resource to both, filters tenant_id, tag_id = ANY($2) and shared_with_user_id = $3, orders by updated_at DESC and takes 50. Pages come back with fewer than 50 distinct resources and the total in the header is far too high. Explain the row multiplication, rewrite both the page query and the count query so each is correct, and name the index each one needs. PostgreSQL 16.

Approach

Do the arithmetic against the predicates that are actually there. An inner join emits one row per matching child row, and both joins are filtered: tag_id = ANY($2) admits only the requested tags, shared_with_user_id = $3 admits one user's share rows. So a resource holding three of the requested tags and shared with $3 once yields three rows, not one — the multiplier is its count of matching tags times its share rows for that single user, and that second factor is 1 unless the table admits duplicate (resource_id, shared_with_user_id) pairs. LIMIT 50 then limits rows rather than resources, and COUNT(*) counts pairs — the header is the product, not the population.
Reject DISTINCT as the fix. It deduplicates after the product has been built, so the planner must materialise and sort the fanned-out set before the LIMIT can apply, and it leaves any SUM or AVG in the same select list wrong.
Rewrite both filters as semi-joins, keeping resource as the only row source: AND EXISTS (SELECT 1 FROM resource_tag rt WHERE rt.resource_id = r.resource_id AND rt.tag_id = ANY($2)) and the same shape against resource_share. A semi-join stops at the first match per resource and preserves the driving index order, so ORDER BY updated_at DESC, resource_id DESC LIMIT 50 still stops after 50 rows.
Count with the same predicates and no join at all: SELECT count(*) FROM resource r WHERE r.tenant_id = $1 AND r.status = 'active' AND EXISTS (...) AND EXISTS (...). Nothing multiplies a resource, so the number is the population.

Follow-up

The filter changes from 'any of these tags' to 'all of these tags'. Rewrite it and state what it costs relative to the ANY form.
A resource can be shared with the same user twice under different permissions. Does your count change, and should it?

Keep soft-deleted accounts from blocking re-registration

Easy · soft delete · unique constraints · engine differences

app_user holds user_id, tenant_id, email CITEXT, password_hash (NULL for SSO principals), email_verified_at, auth_version, status ('invited','active','suspended','deactivated'), created_at, updated_at, deleted_at. Two live accounts for one address inside a tenant must be impossible, but an address freed by a soft delete must be reusable, and the same tenant may delete and re-register it repeatedly. Write the uniqueness DDL for PostgreSQL 16, then the equivalent for MySQL 8 where partial indexes do not exist, and say what each permits once three deleted rows already hold that address.

Approach

Start from what is actually unique: not (tenant_id, email), but (tenant_id, email) among live rows. PostgreSQL says that directly — CREATE UNIQUE INDEX app_user_live_email ON app_user (tenant_id, email) WHERE deleted_at IS NULL. A full constraint over the same two columns burns the address permanently the first time someone deletes an account.
Keep case-insensitivity in the type or the index, never in the application: CITEXT as given, or UNIQUE (tenant_id, lower(email)) as an expression index where the extension is unavailable. A case-sensitive unique column is exactly how two accounts for one human appear.
For MySQL 8 the predicate has to move inside the key: add a discriminator column that is a constant 0 while the row is live and is set to user_id on delete, with UNIQUE (tenant_id, email, deleted_marker). Live rows share the constant and still collide; deleted rows differ from each other and stop colliding.
State the NULL variant and its dependency: leaving the marker NULL for deleted rows also works, because a unique index treats NULLs as distinct — true in MySQL, and true in PostgreSQL only under the default NULLS DISTINCT, which PostgreSQL 15 lets you reverse. Check the polarity against the three existing deleted rows: constant-on-live is what preserves the collision you want, and reversing it silently admits duplicate live accounts.

Follow-up

A deleted account re-registers with the same address the next day. Do the old resource rows follow the new user_id, and how does the API keep the two principals apart?
How do you honour an erasure request while resource_revision.actor_user_id still references this table?

Can you walk me through the most complex project you have contributed to recently?

Medium · Technical and Project Experience

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?

Which specific technologies from your resume were most critical to your previous project’s success?

Medium · Technical and Project Experience

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 ensure your code is maintainable and scalable?

Medium · Technical and Project Experience

Approach

Fix the scope first: who calls this, how often, and what they do when it fails.
Name the read and write paths separately; they rarely have the same bottleneck.
Choose a partition key and say what query it makes expensive.
State the consistency you need, and where you are willing to be stale.

Follow-up

What breaks first when traffic grows ten times?
How does this behave when that dependency is down for an hour?

How would you design a simple component to retrieve data from an API?

Medium · Practical Coding and Problem Solving

Approach

Fix the scope first: who calls this, how often, and what they do when it fails.
Name the read and write paths separately; they rarely have the same bottleneck.
Choose a partition key and say what query it makes expensive.
State the consistency you need, and where you are willing to be stale.

Follow-up

What breaks first when traffic grows ten times?
How does this behave when that dependency is down for an hour?

How do you approach debugging or troubleshooting a system that is failing in production?

Medium · Technical and Project Experience

Approach

Establish what changed and when, before forming any theory.
Pick a bisection that eliminates candidates whichever way it turns out.
Check the instrumentation before believing the symptom.
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 First Horizon candidates report.

Day 1 — Map the First Horizon loop

Write out the reported sequence: Recruiter Screening, Technical Assessments, Managerial Discussions.
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 Software Engineering (general)

Spend the session on Software Engineering (general), which First Horizon candidates report being tested on.
Write one worked example in Software Engineering (general) and time yourself on it.

Deliverable: One timed worked example in Software Engineering (general).

Day 3 — Work Technical Interviewing (problem-solving tasks)

Spend the session on Technical Interviewing (problem-solving tasks), which First Horizon candidates report being tested on.
Write one worked example in Technical Interviewing (problem-solving tasks) and time yourself on it.

Deliverable: One timed worked example in Technical Interviewing (problem-solving tasks).

Day 4 — Work Coding Exercises / Code Tests

Spend the session on Coding Exercises / Code Tests, which First Horizon candidates report being tested on.
Write one worked example in Coding Exercises / Code Tests and time yourself on it.

Deliverable: One timed worked example in Coding Exercises / Code Tests.

Day 5 — Answer out loud: Technical and Project Experience

Answer aloud, timed: Can you walk me through the most complex project you have contributed to recently?
Answer aloud, timed: Which specific technologies from your resume were most critical to your previous project’s success?

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

Day 6 — Answer out loud: Behavioral and Situational

Answer aloud, timed: Describe a time you disagreed with a technical decision made by a team lead. How did you handle it?
Answer aloud, timed: How do you handle feedback from a manager or peer during a code review?

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

Day 7 — Answer out loud: Practical Coding and Problem Solving

Answer aloud, timed: Can you walk me through your thought process for solving a common data handling task in your primary language?
Answer aloud, timed: How would you design a simple component to retrieve data from an API?

Deliverable: Spoken answers to 2 reported Practical Coding and Problem Solving question(s), under time.

Behavioural preparation

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

Describe a time you had to learn a new tool or framework under a tight deadline.

Medium · Technical and Project Experience

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?