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Merge Software Engineer Interview Guide

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

The 60-second brief

As a Software Engineer on the Experience Engineering team at Merge, you will play a critical role in shaping the developer-facing products that power the modern integration ecosystem. Merge is the leading provider of agentic tools and customer-facing integrations, trusted by frontier LLM providers, Fortune 500 organizations, and top-tier B2B SaaS companies. The Experience Engineering team is a full-stack, product-driven group tasked with making highly complex, multi-platform integrations feel seamless, reliable, and intuitive for thousands of developers worldwide. In this role, you will work directly on the core surfaces that define the Merge developer experience, including the customer-facing dashboard, comprehensive documentation, APIs, and SDKs.

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

Focus areas

  • Backend engineering
  • Full stack engineering
  • API development

The Merge interview process

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

Recruiter Screen

Initial screening call with a recruiter to assess candidate fit and discuss the role.

What to demonstrate

  • Initial screening call with a recruiter to assess candidate fit and discuss the role
  • Depth in Backend engineering

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 Screening

Assessment of core coding capabilities through technical questions or exercises.

What to demonstrate

  • Assessment of core coding capabilities through technical questions or exercises
  • Depth in Backend engineering

How to prepare

  • Answer aloud and timed: Solve a classic string manipulation or array-based LeetCode Medium problem, ensuring you walk through your edge cases and optimize for time complexity.
  • Answer aloud and timed: Explain the difference between composition and inheritance, and write a class structure that demonstrates how you would model a reusable integration connector.

Virtual Onsite Loop

Multiple deep-dive technical sessions and a dedicated behavioral round conducted virtually.

What to demonstrate

  • Multiple deep-dive technical sessions and a dedicated behavioral round conducted virtually
  • Depth in Backend engineering

How to prepare

  • Answer aloud and timed: What specific web frameworks (such as Django, Rails, or React) have you used extensively, and what are the major architectural trade-offs of those technologies?
  • Answer aloud and timed: Describe a complex database schema you designed in Postgres. How did you handle indexing, scaling, and query optimization as data volume grew?

Executive Involvement

Final stages of the interview include participation from executive leadership or founders.

What to demonstrate

  • Final stages of the interview include participation from executive leadership or founders
  • Depth in Backend engineering

How to prepare

  • Answer aloud and timed: What has been the most technically challenging problem you have solved in your career so far, and what did you learn from the outcome?
  • Answer aloud and timed: How do you manage state and maintain high performance when building highly interactive frontend components in a framework like React?

Where candidates lose points

Do your homework on the product

Before your first interview, sign up for a demo or read through the Merge API documentation thoroughly. Understand the difference between Merge Unified and Merge Agent Handler. Being able to speak intelligently about their core product offerings will instantly set you apart.

Prepare your "Why Merge" story

The behavioral interviews place an exceptionally heavy emphasis on this question. Be ready to explain why you are passionate about integrations, developer tools, or the AI agent ecosystem, and how your background aligns with this mission.

Think like a product owner

During system design and coding rounds, do not just focus on the code. Discuss the user experience, how developers will interact with your API endpoints, and how your technical decisions impact the overall product reliability.

Questions & practice

Implement an algorithm to find the shortest path or relationship chain between two nodes in a network, simulat

Medium · Coding & Algorithmic Problem Solving

Implement an algorithm to find the shortest path or relationship chain between two nodes in a network, simulating how Merge maps data across different platforms.

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 classic string manipulation or array-based LeetCode Medium problem, ensuring you walk through your edg

Medium · Coding & Algorithmic Problem Solving

Solve a classic string manipulation or array-based LeetCode Medium problem, ensuring you walk through your edge cases and optimize for time complexity.

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?

Canonicalise a request body into a stable idempotency fingerprint

Medium · parsing · canonicalisation · hashing

idempotency_key.request_fingerprint is a SHA-256 over the method, path and canonicalised body, and a retry whose fingerprint differs must be rejected with 422 rather than served the stored response. Write the canonicaliser. Bodies are JSON up to 256 KB nested at most 32 levels; clients vary key order, whitespace and unicode escaping, and some send 64-bit ids as JSON numbers. Produce a deterministic byte string such that semantically identical bodies match and any semantic difference does not. State your complexity and name two normalisations you refuse to perform.

Approach

  1. Parse once into a tree, then re-serialise under fixed rules: object keys sorted, array order preserved, one escaping convention, no insignificant whitespace. Parsing is O(n) and sorting keys is O(k log k) per object, so O(n log n) overall with O(depth) stack, and the 32-level cap is enforced during parsing because hostile nesting is how a canonicaliser becomes a stack overflow.
  2. Sort keys by their UTF-8 bytes and say why the obvious implementation is wrong in some runtimes: a default string comparison that orders by UTF-16 code units places surrogate pairs, meaning code points from U+10000 up, below U+E000 to U+FFFF, which is not UTF-8 byte order, so two services written in different languages disagree on the same document.
  3. Do not re-encode numbers through a double. IEEE-754 binary64 represents integers exactly only up to 2^53, so normalising a 19-digit id through a float changes it, and 1 against 1.0 cannot be reconciled without deciding whether they are the same value. Preserve the literal token, and require ids as strings at the API boundary if you want them comparable.
  4. Reject duplicate keys rather than picking one. JSON permits them and parsers disagree, most keeping the last, so any choice you make ties the fingerprint to a parser detail that the code handling the request does not necessarily share.

Follow-up

  • A client sends the same logical request with an extra field your API ignores. Same key, different fingerprint, so you return 422. Is that the right answer?
  • Where does the fingerprint get computed relative to request decompression and the body-size limit?

Describe a complex database schema you designed in Postgres. How did you handle indexing, scaling, and query o

Medium · Technical Background & System Alignment

Describe a complex database schema you designed in Postgres. How did you handle indexing, scaling, and query optimization as data volume grew?

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?

Replace offset paging on the resource feed with keyset

Easy · keyset pagination · composite index · sort order

resource holds resource_id, tenant_id, owner_user_id, title, body_ref, version, status ('draft','active','archived','deleted'), created_at, updated_at, deleted_at, with an index on (tenant_id, status, updated_at DESC, resource_id DESC). The listing endpoint returns active resources for one tenant, newest update first, 50 per page, today with LIMIT 50 OFFSET n. Tenants reach page 400 and rows are created while they read. Write the keyset query, define what the cursor carries and how it is encoded, and say which part of the index each predicate uses. Assume PostgreSQL 16.

Approach

  1. Name the two failures separately. OFFSET 20000 makes the server produce and discard 20,000 rows, so page cost grows with depth rather than with page size. Independently, any write that changes how many rows sort above the offset moves the window between two fetches, and the direction decides which anomaly you get: an insert lands at the head of updated_at DESC and pushes already-returned rows down past the boundary, so they are returned a second time; a delete above the offset, or a row whose updated_at is bumped above the cursor, pulls rows up and one is never returned at all. Nothing in the response reveals either.
  2. Write the seek: WHERE tenant_id = $1 AND status = 'active' AND (updated_at, resource_id) < ($2, $3) ORDER BY updated_at DESC, resource_id DESC LIMIT 50. The row-value comparison is one index range rather than a disjunction, and both columns are NOT NULL, which is what makes that comparison well defined.
  3. Map each predicate onto the index: tenant_id and status are equality on the leading columns, (updated_at, resource_id) is the range, and the ORDER BY matches the index order so no Sort node appears and the scan stops after 50 rows. The DESC in the definition only matters for mixed directions — a plain ascending btree on the same columns is read backwards for this query.
  4. Put both sort columns in the cursor and nothing the client can tamper with into another tenant: base64 of (updated_at, resource_id), validated server-side, with tenant_id taken from the principal.

Follow-up

  • The client asks for 'jump to page 400'. What do you offer instead, and what does the honest version cost?
  • Sort order becomes user-selectable across four columns. How many indexes is that, and which would you refuse to add?

Design a parser that can ingest varying third-party API payloads and normalize them into a single, unified dat

Medium · Coding & Algorithmic Problem Solving

Design a parser that can ingest varying third-party API payloads and normalize them into a single, unified data structure.

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?

Explain the difference between composition and inheritance, and write a class structure that demonstrates how

Medium · Coding & Algorithmic Problem Solving

Explain the difference between composition and inheritance, and write a class structure that demonstrates how you would model a reusable integration connector.

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?

What specific web frameworks (such as Django, Rails, or React) have you used extensively, and what are the maj

Medium · Technical Background & System Alignment

What specific web frameworks (such as Django, Rails, or React) have you used extensively, and what are the major architectural trade-offs of those technologies?

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?

What has been the most technically challenging problem you have solved in your career so far, and what did you

Medium · Technical Background & System Alignment

What has been the most technically challenging problem you have solved in your career so far, and what did you learn from the outcome?

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 manage state and maintain high performance when building highly interactive frontend components in

Medium · Technical Background & System Alignment

How do you manage state and maintain high performance when building highly interactive frontend components in a framework like React?

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?

Why do you want to work at Merge, and what excites you most about the API integration and LLM agent tooling sp

Medium · Behavioral & Cultural Fit

Why do you want to work at Merge, and what excites you most about the API integration and LLM agent tooling space?

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?

Describe a situation where you had to interact with a customer or a non-technical stakeholder to resolve a cri

Medium · Behavioral & Cultural Fit

Describe a situation where you had to interact with a customer or a non-technical stakeholder to resolve a critical production issue.

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 Merge candidates report.

Day 1 — Map the Merge loop

  • Write out the reported sequence: Recruiter Screen, Technical Screening, Virtual Onsite Loop, Executive Involvement.
  • 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 Backend engineering

  • Spend the session on Backend engineering, which Merge candidates report being tested on.
  • Write one worked example in Backend engineering and time yourself on it.

Deliverable: One timed worked example in Backend engineering.

Day 3 — Work Full stack engineering

  • Spend the session on Full stack engineering, which Merge candidates report being tested on.
  • Write one worked example in Full stack engineering and time yourself on it.

Deliverable: One timed worked example in Full stack engineering.

Day 4 — Work API development

  • Spend the session on API development, which Merge candidates report being tested on.
  • Write one worked example in API development and time yourself on it.

Deliverable: One timed worked example in API development.

Day 5 — Answer out loud: Coding & Algorithmic Problem Solving

  • Answer aloud, timed: Implement an algorithm to find the shortest path or relationship chain between two nodes in a network, simulating how Merge maps data across different platforms.
  • Answer aloud, timed: Design a parser that can ingest varying third-party API payloads and normalize them into a single, unified data structure.

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

Day 6 — Answer out loud: Technical Background & System Alignment

  • Answer aloud, timed: What specific web frameworks (such as Django, Rails, or React) have you used extensively, and what are the major architectural trade-offs of those technologies?
  • Answer aloud, timed: Describe a complex database schema you designed in Postgres. How did you handle indexing, scaling, and query optimization as data volume grew?

Deliverable: Spoken answers to 2 reported Technical Background & System Alignment question(s), under time.

Day 7 — Answer out loud: Behavioral & Cultural Fit

  • Answer aloud, timed: Why do you want to work at Merge, and what excites you most about the API integration and LLM agent tooling space?
  • Answer aloud, timed: Tell me about a time when you had to deal with significant ambiguity on a project. How did you unblock yourself and deliver the project on time?

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

Behavioural preparation

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

Tell me about a time when you had to deal with significant ambiguity on a project. How did you unblock yoursel

Medium · Behavioral & Cultural Fit

Tell me about a time when you had to deal with significant ambiguity on a project. How did you unblock yourself and deliver the project on time?

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 constructive feedback from a peer or manager during a code review or architectural discussio

Medium · Behavioral & Cultural Fit

How do you handle constructive feedback from a peer or manager during a code review or architectural discussion?

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?

Reverse your own decision and price the reversal

Medium · reversibility · measurement · migrations

Describe a technical decision you made and later reversed. Pick one that cost something: a service you split and merged back, a cache you added and removed, an index you created that pushed the planner onto a worse plan, a projection you rebuilt from scratch. State what you believed when you decided, the measurement that changed your mind, how long the wrong version ran in production, and what the reversal cost in migrations, dual writes, and a deprecation window for callers you did not own.

Approach

  1. State the original rationale without irony, in the version you would still defend given what was known then. If it is not defensible, the story is about carelessness rather than judgement, and a different example serves you better.
  2. Give the measurement that moved with a before and after: the p99 that did not improve, the cache hit rate that sat at 40%, the plan that flipped to a sequential scan once the table passed a size you can name.
  3. Cost the reversal in steps, not adjectives: expand-and-contract deploys, the dual-write window, the callers who had to be notified, the rows already written in the wrong shape that had to be backfilled or abandoned.
  4. Distinguish reversal from rewrite by naming what you kept. Most good reversals preserve the schema or the interface and undo one decision inside it, which is also why they were affordable.

Follow-up

  • What in that decision was irreversible, and did you know it was irreversible when you made it?
  • How did you tell the people who had already built on top of the original decision?