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J&B Medical Supply Software Engineer Interview Guide

J&B Medical Supply Software Engineer interview guide: reported rounds, questions and how candidates describe the process.

The 60-second brief

A Software Engineer at J&B Medical Supply plays a critical role in driving the technology behind one of the nation's premier medical distribution and healthcare commerce platforms. In this position, you are responsible for designing, developing, and maintaining high-performance systems that manage complex inventory, streamline order fulfillment, and support critical healthcare transactions. The software you build directly impacts millions of patients and healthcare providers who rely on the timely and accurate delivery of medical supplies. The engineering team at J&B Medical Supply tackles challenges at the intersection of logistics, e-commerce, and healthcare compliance. This requires building highly scalable RESTful APIs, optimizing database operations, and ensuring robust system integrations across multiple platforms.

This guide is scoped to a Software Engineer candidate at J&B Medical Supply.

Focus areas

  • Behavioral Interviewing
  • Technical Interviewing
  • Coding Challenges

The J&B Medical Supply interview process

J&B Medical Supply candidates report 4 rounds over 3-5 weeks. The stages below are what candidates describe, not a published process.

Recruiter Phone Screen

Initial call to review your background, salary expectations, and overall fit for the role.

What to demonstrate

  • Initial call to review your background, salary expectations, and overall fit for the role
  • Depth in Behavioral Interviewing

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.

Online Technical Assessment

Complete a coding and database skills assessment, typically via HackerRank.

What to demonstrate

  • Complete a coding and database skills assessment, typically via HackerRank
  • Depth in Behavioral Interviewing

How to prepare

  • Answer aloud and timed: What are the core annotations used to create a REST controller in Spring Boot, and what do they do?
  • Answer aloud and timed: Describe how dependency injection works in the Spring Framework and why it is beneficial.

Technical and Behavioral Panel Interviews

Participate in interviews with engineering managers and senior team members focusing on technical and behavioral aspects.

What to demonstrate

  • Participate in interviews with engineering managers and senior team members focusing on technical and behavioral aspects
  • Depth in Behavioral Interviewing

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

Final Round Panel

For senior positions, engage in a comprehensive multi-hour panel covering system design, live coding, and leadership discussions.

What to demonstrate

  • For senior positions, engage in a comprehensive multi-hour panel covering system design, live coding, and leadership discussions
  • Depth in Behavioral Interviewing

How to prepare

  • Answer aloud and timed: How would you optimize a search algorithm to run in logarithmic time instead of linear time?
  • Answer aloud and timed: Write a program to sort a collection of objects based on a specific attribute using C# or Java.

Where candidates lose points

Know Your Resume Inside Out

Be ready to explain every project, technology, and architectural decision listed on your resume. Interviewers will ask you to dive deep into your past experiences.

Focus on the "Why

When explaining your technical solutions, don't just describe what you did. Explain why you chose that specific approach, what trade-offs you considered, and how it benefited the business.

Prepare for Live Code Reviews

Practice looking at code written by others, identifying inefficiencies or bugs, and explaining how to improve it. This is a common format used during their technical rounds.

Ask Thoughtful Questions

At the end of your interviews, ask questions about their technology stack, team structure, and upcoming projects. This demonstrates your genuine interest in the role and the company's future.

Questions & practice

Given a list of integers, write a function to identify and return all duplicate values.

Medium · Data Structures & 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 optimize a search algorithm to run in logarithmic time instead of linear time?

Medium · Data Structures & 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?

Write a program to sort a collection of objects based on a specific attribute using C# or Java.

Medium · Data Structures & 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?

What is the difference between a HashMap and a TreeMap, and when would you use each?

Medium · Data Structures & 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?

Given a string, how would you check if it is a palindrome using an iterative approach?

Medium · Data Structures & 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 do you write a SQL query to find the second-highest order value from a transactions table?

Medium · Databases & SQL

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?

Explain the difference between optimistic and pessimistic locking in Hibernate.

Medium · Java and Spring Boot Ecosystem

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 are the core annotations used to create a REST controller in Spring Boot, and what do they do?

Medium · Java and Spring Boot Ecosystem

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 how dependency injection works in the Spring Framework and why it is beneficial.

Medium · Java and Spring Boot Ecosystem

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 configure a custom timezone property in a Spring Boot model class?

Medium · Java and Spring Boot Ecosystem

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?

Explain the differences between inner, left, and right joins with practical examples.

Medium · Databases & SQL

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 are database indexes, and how do they affect read and write performance?

Medium · Databases & SQL

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?

Describe a scenario where you would use a database transaction and how you ensure ACID compliance.

Medium · Databases & SQL

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?

Describe a project where you had to make a critical system design decision. What was the outcome?

Medium · Behavioral & Scenario-Based

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?

Exports duplicate a row range about once a week

Hard · leases · clock skew · idempotency

Roughly once a week an export writes a file containing a duplicated range of rows. The affected job_run rows show attempt = 1, status = succeeded, one started_at, and a lease_owner naming a different host from the one whose logs show the job starting. Leases last 30 seconds and are heartbeated every 10 from inside the handler; lease_expires_at is computed on the worker and compared against the database's now(). Find the mechanism, and give a fix that holds even if you cannot fix the clocks.

Approach

  1. Start from the fact that eliminates the obvious answer. attempt = 1 means no retry was recorded, so this is not a re-run after failure; two workers ran the same row concurrently and the takeover path never touched the counter. lease_owner naming a host other than the one that started the job is the same statement from the other side.
  2. Enumerate the mechanisms that cause a premature takeover, then find the signal that separates them. Either the lease genuinely expired because the heartbeat did not fire, which is what happens when the heartbeat runs on the handler's own thread and the handler makes a long blocking call, or it only appeared expired because two clocks disagree, since lease_expires_at is written from the worker's clock and evaluated against the database's. The discriminator is the distribution: incidents clustered on the longest exports indict the heartbeat, incidents clustered on one host indict skew. Measure both, and measure each host's offset against the database directly.
  3. Read the reclaim query precisely. In PostgreSQL now() is transaction start time, not statement time, so a reclaimer holding a long transaction compares against an older timestamp than expected; clock_timestamp() is the statement-time function. This is worth ruling in or out before you redesign anything, because it changes which rows look expired.
  4. Remove the second clock rather than trying to synchronise it. Issue and extend the lease in the database, with lease_expires_at = now() + interval '30 seconds' in both the claim and the heartbeat, so exactly one clock is ever compared and worker skew stops mattering to this predicate.

Follow-up

  • The displaced worker has already streamed half the file to object storage. What makes that side effect safe to repeat?
  • You now count takeovers. What alert fires on that counter, and at what threshold?

Suggested practice checklist

Built from the rounds and topics J&B Medical Supply candidates report.

Day 1 — Map the J&B Medical Supply loop

  • Write out the reported sequence: Recruiter Phone Screen, Online Technical Assessment, Technical and Behavioral Panel Interviews, Final Round 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 Behavioral Interviewing

  • Spend the session on Behavioral Interviewing, which J&B Medical Supply candidates report being tested on.
  • Write one worked example in Behavioral Interviewing and time yourself on it.

Deliverable: One timed worked example in Behavioral Interviewing.

Day 3 — Work Technical Interviewing

  • Spend the session on Technical Interviewing, which J&B Medical Supply candidates report being tested on.
  • Write one worked example in Technical Interviewing and time yourself on it.

Deliverable: One timed worked example in Technical Interviewing.

Day 4 — Work Coding Challenges

  • Spend the session on Coding Challenges, which J&B Medical Supply candidates report being tested on.
  • Write one worked example in Coding Challenges and time yourself on it.

Deliverable: One timed worked example in Coding Challenges.

Day 5 — Answer out loud: Java and Spring Boot Ecosystem

  • Answer aloud, timed: Explain the difference between optimistic and pessimistic locking in Hibernate.
  • Answer aloud, timed: How do you handle exceptions globally in a Spring Boot application?

Deliverable: Spoken answers to 2 reported Java and Spring Boot Ecosystem question(s), under time.

Day 6 — Answer out loud: Data Structures & Algorithms

  • Answer aloud, timed: Given a list of integers, write a function to identify and return all duplicate values.
  • Answer aloud, timed: How would you optimize a search algorithm to run in logarithmic time instead of linear time?

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

Day 7 — Answer out loud: Databases & SQL

  • Answer aloud, timed: How do you write a SQL query to find the second-highest order value from a transactions table?
  • Answer aloud, timed: Explain the differences between inner, left, and right joins with practical examples.

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

Behavioural preparation

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

How do you handle exceptions globally in a Spring Boot application?

Medium · Java and Spring Boot Ecosystem

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 schema migrations in a production environment without causing downtime?

Medium · Databases & SQL

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 to debug a complex issue in a production environment under a tight deadline.

Medium · Behavioral & Scenario-Based

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 a situation where you disagree with a teammate on a technical implementation?

Medium · Behavioral & Scenario-Based

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?

Walk me through your experience working in an Agile/Scrum environment.

Medium · Behavioral & Scenario-Based

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 personal programming project you worked on recently and the technical challenges you overcame.

Medium · Behavioral & Scenario-Based

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?