Chainbridge Solutions Software Engineer Interview Guide

The 60-second brief

As a Software Engineer at Chainbridge Solutions, you play a pivotal role in developing innovative software solutions that meet the complex needs of our clients, particularly in the litigation and cybersecurity domains. Your work directly impacts the effectiveness and efficiency of our products, ensuring they deliver value to users while maintaining the highest standards of security and reliability. This position is critical as it not only contributes to the technical backbone of our services but also influences strategic decisions that drive business growth. In this role, you will engage with cross-functional teams, leveraging your technical expertise to solve real-world problems and enhance our software offerings. You will have the opportunity to work on diverse projects, from developing new features for our existing platforms to architecting solutions for new initiatives.

This guide is scoped to a Software Engineer candidate at Chainbridge Solutions.

Focus areas

• Technical Cybersecurity Fundamentals
• Coding Ability Testing
• Problem Solving

The Chainbridge Solutions interview process

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

Initial Screening

Candidates undergo an initial screening with HR to assess fit for the role.

What to demonstrate

• Candidates undergo an initial screening with HR to assess fit for the role
• Depth in Technical Cybersecurity Fundamentals

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

Candidates participate in technical assessments, which may include coding tests and problem-solving scenarios.

What to demonstrate

• Candidates participate in technical assessments, which may include coding tests and problem-solving scenarios
• Depth in Technical Cybersecurity Fundamentals

How to prepare

• Answer aloud and timed: Describe your experience with cybersecurity practices in software development.
• Answer aloud and timed: How do you ensure code quality and maintainability in your projects?

Technical and Behavioral Interviews

Interviews that evaluate both technical skills and behavioral components to understand collaboration and user focus.

What to demonstrate

• Interviews that evaluate both technical skills and behavioral components to understand collaboration and user focus
• Depth in Technical Cybersecurity Fundamentals

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 technical and behavioral interviews above and write down what you would ask to confirm before it.

Where candidates lose points

Practice Coding

Regular coding practice is essential, particularly with algorithms and data structures. Utilize online platforms to refine your skills.

Prepare for Behavioral Questions

Reflect on your past experiences and be ready to discuss them in the context of teamwork, challenges, and successes.

Understand the Company

Familiarize yourself with Chainbridge Solutions’ mission and values. This will help you align your answers with the company culture during interviews.

Ask Questions

Prepare thoughtful questions to ask your interviewers. This not only demonstrates your interest but also helps you assess whether the role is a good fit for you.

Questions & practice

Can you explain the difference between synchronous and asynchronous programming?

Medium · Technical / Domain Questions

Approach

1. Say what the runtime actually does before reasoning about the code.
2. Name what is shared across threads and what owns each piece of state.
3. Identify the window where an invariant is briefly untrue.
4. Distinguish a value from a reference to it, and say which one you handed out.

Follow-up

• What happens if two callers reach this at the same time?
• Where could this allocate more than you expect?

Write a function to reverse a string in your preferred programming language.

Medium · Coding / Algorithms

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?

Explain the concept of Big O notation and provide examples of time complexity.

Medium · Coding / Algorithms

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?

Solve a common algorithm problem, such as finding the shortest path in a graph.

Medium · Coding / Algorithms

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 basic authentication system for a web application?

Medium · Coding / Algorithms

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?

Describe how you would optimize a slow-running database query.

Medium · Problem-Solving / Case Studies

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?

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

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

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?

How do you ensure code quality and maintainability in your projects?

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 would you approach designing a new feature for a legal software application?

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?

If you were given an underperforming application, what steps would you take to diagnose the issues?

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 handle a situation where a project deadline is at risk?

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?

What is your approach to debugging complex issues?

Medium · Technical / Domain Questions

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 Chainbridge Solutions candidates report.

Day 1 — Map the Chainbridge Solutions loop

• Write out the reported sequence: Initial Screening, Technical Assessments, Technical and Behavioral Interviews.
• 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 Technical Cybersecurity Fundamentals

• Spend the session on Technical Cybersecurity Fundamentals, which Chainbridge Solutions candidates report being tested on.
• Write one worked example in Technical Cybersecurity Fundamentals and time yourself on it.

Deliverable: One timed worked example in Technical Cybersecurity Fundamentals.

Day 3 — Work Coding Ability Testing

• Spend the session on Coding Ability Testing, which Chainbridge Solutions candidates report being tested on.
• Write one worked example in Coding Ability Testing and time yourself on it.

Deliverable: One timed worked example in Coding Ability Testing.

Day 4 — Work Problem Solving

• Spend the session on Problem Solving, which Chainbridge Solutions candidates report being tested on.
• Write one worked example in Problem Solving and time yourself on it.

Deliverable: One timed worked example in Problem Solving.

Day 5 — Answer out loud: Technical / Domain Questions

• Answer aloud, timed: What programming languages are you most comfortable with, and why?
• Answer aloud, timed: Can you explain the difference between synchronous and asynchronous programming?

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

Day 6 — Answer out loud: Behavioral / Leadership

• Answer aloud, timed: Describe a time when you faced a significant challenge in a project. How did you handle it?
• Answer aloud, timed: How do you prioritize your tasks when working on multiple projects?

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

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

• Answer aloud, timed: How would you approach designing a new feature for a legal software application?
• Answer aloud, timed: If you were given an underperforming application, what steps would you take to diagnose the issues?

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 your experience with cybersecurity practices in software development.

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?

Describe a time when you faced a significant challenge in a project. How did you handle it?

Medium · Behavioral / Leadership

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 working on multiple projects?

Medium · Behavioral / Leadership

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 how you collaborated with a team to achieve a goal?

Medium · Behavioral / Leadership

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 motivates you to perform well in your role?

Medium · Behavioral / Leadership

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 and criticism?

Medium · Behavioral / Leadership

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?