Gladly Software Engineer Interview Guide

The 60-second brief

At Gladly, we are redefining how brands interact with their customers. Unlike legacy customer service platforms that treat customers as ticket numbers, Gladly is built around a single, lifelong conversation thread. This human-centric approach requires a highly sophisticated, real-time infrastructure capable of consolidating voice, email, chat, SMS, and social messaging into a seamless interface. As a Software Engineer, you will be responsible for building, scaling, and maintaining the core services that power this unified platform. The impact of this role is immediate and far-reaching. You will work on highly concurrent systems, real-time data synchronization, and robust APIs that handle millions of customer interactions daily.

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

Focus areas

• Programming problem solving (general)
• System design
• Coding assessments

The Gladly interview process

Gladly candidates report 7 rounds over 4-6 weeks. The stages below are what candidates describe, not a published process.

Recruiter Screen

Initial discussion to review your background and align on expectations.

What to demonstrate

• Initial discussion to review your background and align on expectations
• Depth in Programming problem solving (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 Screen

Focus on practical coding or API utilization to assess technical skills.

What to demonstrate

• Focus on practical coding or API utilization to assess technical skills
• Depth in Programming problem solving (general)

How to prepare

• Answer aloud and timed: Design a client-side function that interacts with a mocked Gladly API to fetch, filter, and paginate customer conversation history.
• Answer aloud and timed: Given an array of message timestamps and channel types, write an algorithm to merge overlapping active sessions into unified conversation blocks.

Virtual Onsite Loop

Thorough evaluation consisting of four main sessions over one or two days.

What to demonstrate

• Thorough evaluation consisting of four main sessions over one or two days
• Depth in Programming problem solving (general)

How to prepare

• Answer aloud and timed: Design a highly scalable URL shortener service, detailing the database schema, API endpoints, and caching strategy to handle high read-write ratios.
• Answer aloud and timed: Design the API payload and data contract required to sync real-time agent availability status across multiple communication channels.

System Design Session

Assessment of your ability to design systems effectively.

What to demonstrate

• Assessment of your ability to design systems effectively
• Depth in Programming problem solving (general)

How to prepare

• Answer aloud and timed: Sketch out the architecture for a front-end component that displays live-updating chat messages, detailing how the client communicates with the backend.
• Answer aloud and timed: How would you design a rate-limiting middleware for Gladly's external developer APIs to prevent abuse while ensuring high availability?

Product Demo Interview

Evaluation of your understanding and presentation of product-related concepts.

What to demonstrate

• Evaluation of your understanding and presentation of product-related concepts
• Depth in Programming problem solving (general)

How to prepare

• Answer aloud and timed: Describe a complex technical project you owned from end to end. What were the major technical challenges, and how did you overcome them?
• Answer aloud and timed: Tell me about a time you had a strong technical disagreement with a teammate or product manager. How did you resolve it?

Past-Project Presentation

Presentation of a previous project to showcase your experience and skills.

What to demonstrate

• Presentation of a previous project to showcase your experience and skills
• Depth in Programming problem solving (general)

How to prepare

• Answer aloud and timed: Walk me through a situation where you had to debug a critical production issue under tight time constraints.
• Answer aloud and timed: How do you prioritize technical debt versus delivering new features when working on a rapidly evolving product?

Personal Topic Presentation

Engaging presentation on a topic you are passionate about to stand out.

What to demonstrate

• Engaging presentation on a topic you are passionate about to stand out
• Depth in Programming problem solving (general)

How to prepare

• Work Programming problem solving (general) until you can explain it without notes
• Work System design until you can explain it without notes

Where candidates lose points

Clarify system design requirements early

In the system design round, do not jump straight into drawing boxes. Spend the first 5-10 minutes asking clarifying questions about scale, read/write ratios, latency requirements, and specific use cases.

Prioritize your presentation prep

Do not leave your presentations to the last minute. Because communication is highly valued at Gladly, a well-structured, engaging presentation can heavily influence the hiring team's final decision.

Avoid over-engineering your presentation slides before completing your initial technical assessments

Focus your early energy on core coding and system design prep.

Think like an end-user during product rounds

When discussing product features or demos, always tie your technical suggestions back to how they help the customer support agent or the end customer.

Questions & practice

Implement a robust string parser that extracts specific parameters from a raw text stream and formats them int

Medium · Coding & Algorithms

Implement a robust string parser that extracts specific parameters from a raw text stream and formats them into a structured JSON payload.

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?

Write a function to manipulate and clean a series of raw communication log strings, handling malformed inputs

Medium · Coding & Algorithms

Write a function to manipulate and clean a series of raw communication log strings, handling malformed inputs and boundary conditions.

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?

Given an array of message timestamps and channel types, write an algorithm to merge overlapping active session

Medium · Coding & Algorithms

Given an array of message timestamps and channel types, write an algorithm to merge overlapping active sessions into unified conversation blocks.

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?

Write the update path that detects a concurrent edit

Medium · optimistic concurrency · transactional outbox · audit history

resource carries version INT NOT NULL DEFAULT 1. resource_revision holds revision_id, resource_id, version, actor_user_id, change_kind, patch JSONB, request_id, created_at with UNIQUE (resource_id, version). outbox_event holds aggregate_type, aggregate_id, aggregate_version, event_type, payload, status. A PUT carries the version the client read. Write the exact statements for the single transaction that applies the edit, records the revision and enqueues 'resource.updated', and give the handler's branch on zero affected rows. Then say what PostgreSQL 16 does under READ COMMITTED when two of these updates hit one row at once.

Approach

1. One transaction, three writes, no network call inside it: UPDATE resource SET title = $3, version = version + 1, updated_at = now() WHERE resource_id = $1 AND tenant_id = $4 AND version = $2; then INSERT the resource_revision row at version $2 + 1; then INSERT the outbox_event row at the same aggregate_version. The event goes to a table rather than a broker because no transaction spans both.
2. Branch on the affected-row count before doing anything else. Zero has three causes — stale version, wrong tenant, row gone — so re-read once and map to 409 carrying the current version, or 404 for an id outside the caller's tenant, which also stops the endpoint confirming that another tenant's id exists.
3. State the engine behaviour instead of assuming it. Under READ COMMITTED the second UPDATE blocks on the row lock, and when the first commits PostgreSQL re-evaluates the WHERE clause against the newly committed row, so the version predicate now fails and the statement reports zero rows. Under REPEATABLE READ the identical collision raises SQLSTATE 40001 instead, so the handler must fold both shapes into one conflict response.
4. Keep UNIQUE (resource_id, version) even though the predicate already serialises writers. It is what makes a lost update unwritable if any other path ever reaches the revision table, and it converts a logic bug into 23505 rather than into a silently missing history row.

Follow-up

• A client sends the version it read ten minutes ago and the resource has moved three versions. What is in your 409 so it can resolve the conflict without a full re-fetch?
• Two editors, two disjoint fields, no overlap. Does your answer still refuse the second write, 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

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

Design a client-side function that interacts with a mocked Gladly API to fetch, filter, and paginate customer

Medium · Coding & Algorithms

Design a client-side function that interacts with a mocked Gladly API to fetch, filter, and paginate customer conversation history.

Approach

1. Fix the scope first: who calls this, how often, and what they do when it fails.
2. Name the read and write paths separately; they rarely have the same bottleneck.
3. Choose a partition key and say what query it makes expensive.
4. 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?

Design a highly scalable URL shortener service, detailing the database schema, API endpoints, and caching stra

Medium · System & API Design

Design a highly scalable URL shortener service, detailing the database schema, API endpoints, and caching strategy to handle high read-write ratios.

Approach

1. Fix the scope first: who calls this, how often, and what they do when it fails.
2. Name the read and write paths separately; they rarely have the same bottleneck.
3. Choose a partition key and say what query it makes expensive.
4. 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?

Design the API payload and data contract required to sync real-time agent availability status across multiple

Medium · System & API Design

Design the API payload and data contract required to sync real-time agent availability status across multiple communication channels.

Approach

1. Say who the caller is and what they do when the call fails halfway.
2. Define the identity of a request so a retry cannot double-apply it.
3. Separate accepted, pending, failed and confirmed; they are different facts.
4. Design the error taxonomy before the success shape; callers branch on it.

Follow-up

• What happens if the caller retries after a timeout?
• How does a client discover it is on an old version of this contract?

Sketch out the architecture for a front-end component that displays live-updating chat messages, detailing how

Medium · System & API Design

Sketch out the architecture for a front-end component that displays live-updating chat messages, detailing how the client communicates with the backend.

Approach

1. Fix the scope first: who calls this, how often, and what they do when it fails.
2. Name the read and write paths separately; they rarely have the same bottleneck.
3. Choose a partition key and say what query it makes expensive.
4. 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 rate-limiting middleware for Gladly's external developer APIs to prevent abuse while en

Medium · System & API Design

How would you design a rate-limiting middleware for Gladly's external developer APIs to prevent abuse while ensuring high availability?

Approach

1. Fix the scope first: who calls this, how often, and what they do when it fails.
2. Name the read and write paths separately; they rarely have the same bottleneck.
3. Choose a partition key and say what query it makes expensive.
4. 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?

Walk me through a situation where you had to debug a critical production issue under tight time constraints.

Medium · Behavioral & Teamwork

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 Gladly candidates report.

Day 1 — Map the Gladly loop

• Write out the reported sequence: Recruiter Screen, Technical Screen, Virtual Onsite Loop, System Design Session, Product Demo Interview, Past-Project Presentation.
• 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 7 reported rounds, with the weakest marked.

Day 2 — Work Programming problem solving (general)

• Spend the session on Programming problem solving (general), which Gladly candidates report being tested on.
• Write one worked example in Programming problem solving (general) and time yourself on it.

Deliverable: One timed worked example in Programming problem solving (general).

Day 3 — Work System design

• Spend the session on System design, which Gladly candidates report being tested on.
• Write one worked example in System design and time yourself on it.

Deliverable: One timed worked example in System design.

Day 4 — Work Coding assessments

• Spend the session on Coding assessments, which Gladly candidates report being tested on.
• Write one worked example in Coding assessments and time yourself on it.

Deliverable: One timed worked example in Coding assessments.

Day 5 — Answer out loud: Coding & Algorithms

• Answer aloud, timed: Implement a robust string parser that extracts specific parameters from a raw text stream and formats them into a structured JSON payload.
• Answer aloud, timed: Write a function to manipulate and clean a series of raw communication log strings, handling malformed inputs and boundary conditions.

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

Day 6 — Answer out loud: System & API Design

• Answer aloud, timed: Design a highly scalable URL shortener service, detailing the database schema, API endpoints, and caching strategy to handle high read-write ratios.
• Answer aloud, timed: Design the API payload and data contract required to sync real-time agent availability status across multiple communication channels.

Deliverable: Spoken answers to 2 reported System & API Design question(s), under time.

Day 7 — Answer out loud: Behavioral & Teamwork

• Answer aloud, timed: Describe a complex technical project you owned from end to end. What were the major technical challenges, and how did you overcome them?
• Answer aloud, timed: Tell me about a time you had a strong technical disagreement with a teammate or product manager. How did you resolve it?

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

Behavioural preparation

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

Describe a complex technical project you owned from end to end. What were the major technical challenges, and

Medium · Behavioral & Teamwork

Describe a complex technical project you owned from end to end. What were the major technical challenges, and how did you overcome them?

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 had a strong technical disagreement with a teammate or product manager. How did you r

Medium · Behavioral & Teamwork

Tell me about a time you had a strong technical disagreement with a teammate or product manager. How did you resolve it?

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 technical debt versus delivering new features when working on a rapidly evolving product

Medium · Behavioral & Teamwork

How do you prioritize technical debt versus delivering new features when working on a rapidly evolving product?

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?