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Capital Rx Software Engineer Interview Guide

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

The 60-second brief

The Software Engineer role at Capital Rx is pivotal in driving innovative healthcare solutions that enhance patient outcomes and streamline pharmacy benefits management. As a Software Engineer, you will be part of a dynamic team that develops and maintains software applications critical for managing prescription medication processes. Your contributions will directly impact users, including patients and healthcare providers, by ensuring efficient, reliable software that meets their needs in a fast-paced environment. In this role, you'll tackle complex problems related to data processing and integration, working with various technologies to create robust applications. Collaborating closely with product managers, data scientists, and other engineers, you will be tasked with designing scalable solutions that not only meet current demands but also anticipate future challenges.

This guide is scoped to a Software Engineer candidate at Capital Rx.

Focus areas

  • Python
  • Coding Assessments (Take-home tasks)
  • CSV Data Processing

The Capital Rx interview process

Capital Rx candidates report 5 rounds over 4-6 weeks. The stages below are what candidates describe, not a published process.

Initial Screening

Candidates begin with a screening call with a recruiter to assess background and fit.

What to demonstrate

  • Candidates begin with a screening call with a recruiter to assess background and fit
  • Depth in Python

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 Interviews

Multiple rounds of interviews focusing on technical capabilities and problem-solving skills.

What to demonstrate

  • Multiple rounds of interviews focusing on technical capabilities and problem-solving skills
  • Depth in Python

How to prepare

  • Answer aloud and timed: What programming languages are you most proficient in, and why do you prefer them for software development?
  • Answer aloud and timed: How do you ensure code quality and maintainability in your projects?

Behavioral Interviews

Interviews that assess cultural fit and behavioral aspects of the candidate.

What to demonstrate

  • Interviews that assess cultural fit and behavioral aspects of the candidate
  • Depth in Python

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

Technical Deep Dive

In-depth technical discussion to evaluate specific skills and knowledge.

What to demonstrate

  • In-depth technical discussion to evaluate specific skills and knowledge
  • Depth in Python

How to prepare

  • Answer aloud and timed: How do you prioritize your tasks when you're working on multiple projects?
  • Answer aloud and timed: Can you provide an example of how you've worked effectively within a team?

Final Discussion

A concluding conversation with leadership to discuss overall fit and next steps.

What to demonstrate

  • A concluding conversation with leadership to discuss overall fit and next steps
  • Depth in Python

How to prepare

  • Answer aloud and timed: What motivates you to perform at your best in a work environment?
  • Answer aloud and timed: How do you handle feedback and criticism of your work?

Where candidates lose points

Know the Products

Familiarize yourself with Capital Rx products and services to demonstrate your interest and understanding during the interview.

Prepare Your Questions

Have thoughtful questions ready for your interviewers to show your engagement and curiosity about the role and company.

Practice Behavioral Responses

Use the STAR method (Situation, Task, Action, Result) to structure your answers to behavioral questions, providing clear and concise examples.

Show Enthusiasm

Convey your passion for software engineering and how it aligns with Capital Rx's mission to improve healthcare accessibility.

Questions & practice

Present a coding challenge where you need to sort and filter data from a CSV file. Describe your approach.

Medium · Problem-Solving / Case Studies

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 reverse a linked list. Explain your thought process while solving this problem.

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?

What are the time and space complexities of your sorting algorithm of choice? Explain why you chose it.

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?

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?

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?

Describe a challenging technical problem you encountered and how you resolved it.

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?

What programming languages are you most proficient in, and why do you prefer them for software development?

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?

If given a large dataset, how would you approach optimizing its processing and analysis?

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 design a system to manage user authentication and authorization for a web application?

Medium · Problem-Solving / Case Studies

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 do you approach debugging a piece of code that is not functioning as expected?

Medium · Coding / Algorithms

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 Capital Rx candidates report.

Day 1 — Map the Capital Rx loop

  • Write out the reported sequence: Initial Screening, Technical Interviews, Behavioral Interviews, Technical Deep Dive, Final Discussion.
  • 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 5 reported rounds, with the weakest marked.

Day 2 — Work Python

  • Spend the session on Python, which Capital Rx candidates report being tested on.
  • Write one worked example in Python and time yourself on it.

Deliverable: One timed worked example in Python.

Day 3 — Work Coding Assessments (Take-home tasks)

  • Spend the session on Coding Assessments (Take-home tasks), which Capital Rx candidates report being tested on.
  • Write one worked example in Coding Assessments (Take-home tasks) and time yourself on it.

Deliverable: One timed worked example in Coding Assessments (Take-home tasks).

Day 4 — Work CSV Data Processing

  • Spend the session on CSV Data Processing, which Capital Rx candidates report being tested on.
  • Write one worked example in CSV Data Processing and time yourself on it.

Deliverable: One timed worked example in CSV Data Processing.

Day 5 — Answer out loud: Technical / Domain Questions

  • Answer aloud, timed: Explain your experience with RESTful APIs and how you have implemented them in previous projects.
  • Answer aloud, timed: Describe a challenging technical problem you encountered and how you resolved it.

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 obstacle in a project. How did you overcome it?
  • Answer aloud, timed: How do you prioritize your tasks when you're 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: If given a large dataset, how would you approach optimizing its processing and analysis?
  • Answer aloud, timed: Present a coding challenge where you need to sort and filter data from a CSV file. Describe your approach.

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.

Explain your experience with RESTful APIs and how you have implemented them in previous projects.

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?

Discuss your experience with cloud-based solutions and any relevant platforms you have worked with.

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 obstacle in a project. How did you overcome 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 you're 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 provide an example of how you've worked effectively within a team?

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 at your best in a work environment?

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 of your work?

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?