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ACME Software Engineer Interview Guide

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

The 60-second brief

A Software Engineer at ACME is a core driver of technical innovation, responsible for building and scaling the systems that power our global operations. Engineers here work on high-impact projects ranging from robust backend architectures to intuitive, responsive user interfaces. The role demands a balance of deep technical expertise, practical problem-solving, and a product-focused mindset to ensure our services remain reliable, fast, and secure for millions of users daily. At ACME, engineering is not just about writing code; it is about solving complex, real-world problems. You will collaborate closely with cross-functional teams, including product managers, designers, and system architects, to translate business requirements into scalable software solutions.

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

Focus areas

  • API Integration
  • Live Coding
  • Technical Interview

The ACME interview process

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

Resume Screening

Initial review of your resume to assess qualifications and fit for the role.

What to demonstrate

  • Initial review of your resume to assess qualifications and fit for the role
  • Depth in API Integration

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.

Recruiter Call

Discussion with a recruiter to align on your motivations and expectations.

What to demonstrate

  • Discussion with a recruiter to align on your motivations and expectations
  • Depth in API Integration

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 Evaluation

Assessment phase that may include an online aptitude test, take-home coding assignment, or live coding session.

What to demonstrate

  • Assessment phase that may include an online aptitude test, take-home coding assignment, or live coding session
  • Depth in API Integration

How to prepare

  • Answer aloud and timed: Solve a series of mathematical and logical puzzles within a 30-minute window using only paper and a calculator.
  • Answer aloud and timed: Given an array of integers, write an algorithm to find the maximum subarray sum in optimal time complexity.

Interview Panel

Final stage consisting of a deep-dive technical round, system design discussion, and managerial or behavioral conversation.

What to demonstrate

  • Final stage consisting of a deep-dive technical round, system design discussion, and managerial or behavioral conversation
  • Depth in API Integration

How to prepare

  • Answer aloud and timed: Explain how you would implement a custom data structure to track and retrieve elements with specific priority constraints.
  • Answer aloud and timed: Solve a pen-and-paper programming challenge demonstrating your understanding of recursion and memory management.

Where candidates lose points

Communicate your thought process

During live coding, do not code in silence. Talk through your approach, explain why you are choosing a specific data structure, and discuss trade-offs before you start writing code.

Focus on working code first

In practical coding rounds, prioritize getting a working end-to-end solution over writing perfect, hyper-optimized code. You can always refactor and optimize once the core functionality is in place.

Reading the constraints as preamble rather than as part of the problem

The bounds are usually there to eliminate the obvious approach: n up to 10^5 makes an O(n^2) scan roughly 10^10 operations, far outside any per-test time budget, and an input larger than memory rules out loading it at all. When a bound is not given, ask for it, then say out loud which approach it kills.

Questions & practice

Write a clean, well-structured component that handles asynchronous data fetching, loading states, and basic er

Medium · Practical Coding & API Integration

Write a clean, well-structured component that handles asynchronous data fetching, loading states, and basic error handling.

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?

Solve a series of mathematical and logical puzzles within a 30-minute window using only paper and a calculator

Medium · Aptitude & Algorithmic Logic

Solve a series of mathematical and logical puzzles within a 30-minute window using only paper and a calculator.

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 integers, write an algorithm to find the maximum subarray sum in optimal time complexity.

Medium · Aptitude & Algorithmic Logic

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 how you would implement a custom data structure to track and retrieve elements with specific priority

Medium · Aptitude & Algorithmic Logic

Explain how you would implement a custom data structure to track and retrieve elements with specific priority constraints.

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 pen-and-paper programming challenge demonstrating your understanding of recursion and memory managemen

Medium · Aptitude & Algorithmic Logic

Solve a pen-and-paper programming challenge demonstrating your understanding of recursion and memory management.

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?

Why do you want to join ACME as a Software Engineer, and how does this role align with your long-term career g

Medium · Behavioral & Team Collaboration

Why do you want to join ACME as a Software Engineer, and how does this role align with your long-term career goals?

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?

Find version gaps and relay lag with window functions

Medium · window functions · event tables · frame semantics

outbox_event holds event_id, aggregate_type, aggregate_id, aggregate_version, event_type, payload, status ('pending','published','dead'), attempts, created_at, published_at. A projection is missing rows and you must decide whether the relay skipped events or the consumer dropped them. Write three queries over the last seven days: one listing every aggregate_id whose published aggregate_version sequence has a hole, one giving per-day counts with a running total, and one returning the newest published event per aggregate. For each, say where the window function is evaluated relative to WHERE and LIMIT. PostgreSQL 16.

Approach

  1. Gaps: compute lead(aggregate_version) OVER (PARTITION BY aggregate_id ORDER BY aggregate_version) in a subquery, then filter next_version <> aggregate_version + 1 in the outer query. Window functions are evaluated after WHERE, GROUP BY and HAVING and before the outer ORDER BY and LIMIT, so the predicate cannot sit in the same WHERE clause and PostgreSQL 16 has no QUALIFY.
  2. Say what the seven-day filter does to the answer: it truncates every partition, so the first row per aggregate has no predecessor inside the window and a hole spanning the boundary is invisible. Widen the window, or join to resource.version as the authority for the true maximum.
  3. Running total: SELECT date_trunc('day', created_at) AS d, count() AS n, sum(count()) OVER (ORDER BY date_trunc('day', created_at) ROWS UNBOUNDED PRECEDING). An aggregate inside a window call is legal because grouping runs before windowing. The grouping key is unique per row here so ROWS and RANGE agree, but write the frame anyway — over ungrouped rows with tied timestamps the default RANGE frame pulls in every peer row and the total jumps.
  4. Newest per aggregate: DISTINCT ON (aggregate_id) ... ORDER BY aggregate_id, aggregate_version DESC is the cheap PostgreSQL-only form when an index matches that order; row_number() OVER (PARTITION BY aggregate_id ORDER BY aggregate_version DESC) = 1 is the portable form and needs a subquery for the same evaluation-order reason as the gap query.

Follow-up

  • Relay failover redelivers events. Does a duplicate break the gap query, and how would you detect one from this table alone?
  • Turn the gap check into a continuous monitor rather than a query someone runs after an incident. What does it watch?

Build a simple user interface that fetches data from a public news API and displays it dynamically.

Medium · Practical Coding & API Integration

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?

Implement a search and filter system over an API-driven dataset in your frontend framework of choice.

Medium · Practical Coding & API Integration

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?

How do you optimize API request payloads and manage client-side caching to improve UI performance?

Medium · Practical Coding & API Integration

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?

Every query on one table stalls for forty seconds mid-deploy

Medium · lock contention · ddl · migrations

During a release on PostgreSQL, every query touching resource times out for about 40 seconds and then recovers with no intervention. The release ran one migration, ALTER TABLE resource ADD COLUMN archived_reason TEXT, and the migration log shows it completing in 6 ms. Unrelated tables showed no change in error rate. Explain how a 6 ms statement caused a 40-second stall, give the ordered checks you would run on a live system to confirm it, and give the migration procedure that prevents a repeat.

Approach

  1. Separate the statement's duration from the lock's duration. ADD COLUMN with no default is a catalogue-only change and genuinely runs in milliseconds, but it requires ACCESS EXCLUSIVE, and it cannot acquire that until every transaction already touching the table has finished.
  2. Account for the queueing, which is the part that surprises people. A lock request that is waiting blocks later requests for conflicting modes behind it rather than letting them overtake, so one long-open transaction holds the DDL and the DDL holds all the traffic. The stall length is set by the longest open transaction, not by the size of the change.
  3. Confirm on a live system in this order: pg_stat_activity for that table ordered by xact_start, looking for the oldest transaction and specifically for state = idle in transaction; then pg_locks where granted = false to find the waiter; then join them on pid to name blocker and blocked. pg_blocking_pids() does that join for you and is the fastest single call.
  4. Prevent rather than merely time it better. Set lock_timeout to a second or two on the migration session so the DDL abandons the queue after a bounded wait and is retried, instead of holding it for as long as the oldest transaction lives. Be exact about what that buys: queries arriving during the wait still queue behind the pending ACCESS EXCLUSIVE request, so each attempt costs them up to one lock_timeout of added latency. The outage goes from 40 seconds to about one second per attempt, not to zero. Also run migrations away from deploy-time peaks, and put a statement timeout and an idle-in-transaction timeout on the analytics role that opens the long transactions.

Follow-up

  • The same release also wants NOT NULL on that column. What is the sequence that gets there without a long lock?
  • Your lock_timeout retry fails ten times in a row because the analytics transaction is always open. What do you change?

Suggested practice checklist

Built from the rounds and topics ACME candidates report.

Day 1 — Map the ACME loop

  • Write out the reported sequence: Resume Screening, Recruiter Call, Technical Evaluation, Interview Panel.
  • 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 API Integration

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

Deliverable: One timed worked example in API Integration.

Day 3 — Work Live Coding

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

Deliverable: One timed worked example in Live Coding.

Day 4 — Work Technical Interview

  • Spend the session on Technical Interview, which ACME candidates report being tested on.
  • Write one worked example in Technical Interview and time yourself on it.

Deliverable: One timed worked example in Technical Interview.

Day 5 — Answer out loud: Practical Coding & API Integration

  • Answer aloud, timed: Build a simple user interface that fetches data from a public news API and displays it dynamically.
  • Answer aloud, timed: Implement a search and filter system over an API-driven dataset in your frontend framework of choice.

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

Day 6 — Answer out loud: Aptitude & Algorithmic Logic

  • Answer aloud, timed: Solve a series of mathematical and logical puzzles within a 30-minute window using only paper and a calculator.
  • Answer aloud, timed: Given an array of integers, write an algorithm to find the maximum subarray sum in optimal time complexity.

Deliverable: Spoken answers to 2 reported Aptitude & Algorithmic Logic question(s), under time.

Day 7 — Answer out loud: Behavioral & Team Collaboration

  • Answer aloud, timed: Walk me through your academic background and highlight the most challenging technical project you completed.
  • Answer aloud, timed: Describe a time when you had to work with a teammate whose technical approach differed significantly from yours. How did you resolve the conflict?

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

Behavioural preparation

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

Walk me through your academic background and highlight the most challenging technical project you completed.

Medium · Behavioral & Team Collaboration

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 had to work with a teammate whose technical approach differed significantly from your

Medium · Behavioral & Team Collaboration

Describe a time when you had to work with a teammate whose technical approach differed significantly from yours. How did you resolve the conflict?

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 made a mistake in production. What did you learn, and how did you prevent it from hap

Medium · Behavioral & Team Collaboration

Tell me about a time you made a mistake in production. What did you learn, and how did you prevent it from happening again?

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?