A Software Engineer at Mercy is a crucial member of a team that drives technological innovation within the healthcare sector. This role involves designing, developing, and maintaining software applications that support various operational functions, ultimately enhancing patient care and operational efficiency. By leveraging cutting-edge technologies, Software Engineers contribute to projects that directly impact the quality of services provided, ensuring that Mercy remains at the forefront of healthcare technology. The Software Engineer role is not only about coding; it involves collaboration with cross-functional teams, understanding the unique challenges faced in healthcare, and creating solutions that are scalable, secure, and user-friendly. You will work on diverse projects that range from patient management systems to telehealth applications, which require a blend of technical, analytical, and interpersonal skills. This position is ideal for candidates who are passionate about making a difference through technology while enjoying the complexities and challenges that come with the healthcare domain.
Initial Phone Screening
reportedBegin with a phone screening to assess basic qualifications and fit for the role.
What to demonstrate
- Begin with a phone screening to assess basic qualifications and fit for the role
- Depth in Programming
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 Interview
reportedParticipate in an in-depth technical interview to evaluate programming skills and software development knowledge.
What to demonstrate
- Participate in an in-depth technical interview to evaluate programming skills and software development knowledge
- Depth in Programming
How to prepare
- Answer aloud and timed: Can you explain the differences between REST and SOAP APIs?
- Answer aloud and timed: What are the key principles of Agile development, and how have you applied them in your work?
On-site or Virtual Interview
reportedEngage in a comprehensive on-site or virtual interview that includes behavioral assessments and possibly a group discussion or coding challenge.
What to demonstrate
- Engage in a comprehensive on-site or virtual interview that includes behavioral assessments and possibly a group discussion or coding challenge
- Depth in Programming
How to prepare
- Answer aloud and timed: Discuss a challenging technical problem you encountered and how you resolved it.
- Answer aloud and timed: How would you design a system for [specific application, e.g., a patient scheduling system]?
PracHub editorial advice for the preparation topics above.
Understand the Mission
Familiarize yourself with Mercy's mission and values. Being able to articulate how your personal values align with the organization's can significantly enhance your candidacy.
Practice Coding
Utilize online platforms to practice coding challenges. Being well-prepared for live coding interviews can set you apart from other candidates.
Be Ready for Behavioral Questions
Prepare to provide specific examples of your past experiences, focusing on challenges faced and how you overcame them.
Engage with Interviewers
Show genuine interest in the role and ask insightful questions about the team and ongoing projects. This demonstrates your enthusiasm and commitment to joining Mercy.
Choose a category, try a prompt, then open its approach, worked solution or follow-up when you need it.
Write a function to [specific coding task, e.g., reverse a string].
Write a function to [specific coding task, e.g., reverse a string].
Approach
- Restate the input: its shape, its size, and what is guaranteed about it.
- Name the brute-force solution and its complexity before improving on it.
- Choose the data structure from the access pattern, not from familiarity.
- 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 your thought process as you solve a common algorithm problem, such as sorting or searching.
Explain your thought process as you solve a common algorithm problem, such as sorting or searching.
Approach
- Restate the input: its shape, its size, and what is guaranteed about it.
- Name the brute-force solution and its complexity before improving on it.
- Choose the data structure from the access pattern, not from familiarity.
- 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?
Merge partitioned event streams into one ordered feed with bounded lateness
The read-model service consumes 64 log partitions carrying about 4,000 events per second in total. Each partition is ordered within itself, but partitions drift by up to 30 seconds, and the activity feed must present a tenant's events in occurred_at order. Produce the merge. State its complexity, the buffer it requires in events and in bytes, what happens when one partition is idle, and what you do with an event that arrives after you have already emitted its position. Payloads average 1 KB.
Approach
- Merge with a min-heap over the 64 partition heads keyed on (occurred_at, event_id): O(log P) per event and O(n log P) overall. The tie-break on event_id is what makes the output deterministic when two partitions carry the same millisecond, which matters because the feed is paginated and a non-deterministic order reorders pages under the reader.
- Emitting the heap head is only correct once every partition has produced everything up to that timestamp, so the emit condition is a watermark: the minimum across partitions of the highest occurred_at seen, less the allowed lateness. Events are held until the watermark passes them, which is what turns individually ordered streams into a jointly ordered one.
- Size the buffer from the lateness rather than guessing: 4,000 events per second times 30 seconds is 120,000 buffered events, and at 1 KB each about 120 MB of heap. That number is the real price of the ordering guarantee and belongs in front of whoever asked for it.
- Handle the idle partition explicitly, because it fails the feed rather than corrupting it: a partition with no traffic never advances its own maximum, so the watermark freezes and output stops entirely. Either every partition emits a periodic idle marker carrying the broker's current time, or the watermark falls back to wall clock for a partition silent beyond a threshold.
Follow-up
- The lateness budget is raised to five minutes. What is the new buffer, and what besides memory changes?
- The consumer restarts. Where does it resume from, and what does the feed look like for the first 30 seconds?
Find version gaps and relay lag with window functions
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
- 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.
- 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.
- 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.
- 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?
Write the update path that detects a concurrent edit
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
- 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.
- 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.
- 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.
- 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?
Can you explain the differences between REST and SOAP APIs?
Can you explain the differences between REST and SOAP APIs?
Approach
- Say who the caller is and what they do when the call fails halfway.
- Define the identity of a request so a retry cannot double-apply it.
- Separate accepted, pending, failed and confirmed; they are different facts.
- 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 are the key principles of Agile development, and how have you applied them in your work?
What are the key principles of Agile development, and how have you applied them in your work?
Approach
- Clarify what is being asked and what a complete answer contains.
- State your assumptions explicitly before working the problem.
- Say what you would check first and why it is the highest-information step.
- Work from the requirement backwards to the design.
Follow-up
- What assumption would you test first?
- How would you know your answer was wrong?
Discuss a challenging technical problem you encountered and how you resolved it.
Discuss a challenging technical problem you encountered and how you resolved it.
Approach
- Clarify what is being asked and what a complete answer contains.
- State your assumptions explicitly before working the problem.
- Say what you would check first and why it is the highest-information step.
- 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 for [specific application, e.g., a patient scheduling system]?
How would you design a system for [specific application, e.g., a patient scheduling system]?
Approach
- Fix the scope first: who calls this, how often, and what they do when it fails.
- Name the read and write paths separately; they rarely have the same bottleneck.
- Choose a partition key and say what query it makes expensive.
- 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?
Describe the considerations you would take into account when architecting a cloud-based application.
Describe the considerations you would take into account when architecting a cloud-based application.
Approach
- Fix the scope first: who calls this, how often, and what they do when it fails.
- Name the read and write paths separately; they rarely have the same bottleneck.
- Choose a partition key and say what query it makes expensive.
- 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 strategies would you use to ensure data consistency in a distributed system?
What strategies would you use to ensure data consistency in a distributed system?
Approach
- Fix the scope first: who calls this, how often, and what they do when it fails.
- Name the read and write paths separately; they rarely have the same bottleneck.
- Choose a partition key and say what query it makes expensive.
- 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 approach a declining performance issue in a software application?
How would you approach a declining performance issue in a software application?
Approach
- Clarify what is being asked and what a complete answer contains.
- State your assumptions explicitly before working the problem.
- Say what you would check first and why it is the highest-information step.
- 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 steps would you take to gather requirements for a new software feature?
What steps would you take to gather requirements for a new software feature?
Approach
- Clarify what is being asked and what a complete answer contains.
- State your assumptions explicitly before working the problem.
- Say what you would check first and why it is the highest-information step.
- 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 approach debugging a complex software issue?
How do you approach debugging a complex software issue?
Approach
- Establish what changed and when, before forming any theory.
- Pick a bisection that eliminates candidates whichever way it turns out.
- Check the instrumentation before believing the symptom.
- 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?
Built from the rounds and topics Mercy candidates report.
Prepare, practise & reflect
One practical outcome each day. Spend longer where you need it.
0 / 7 done01Map the Mercy loop
- Write out the reported sequence: Initial Phone Screening, Technical Interview, On-site or Virtual Interview.
- 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 3 reported rounds, with the weakest marked.
02Work Programming
- Spend the session on Programming, which Mercy candidates report being tested on.
- Write one worked example in Programming and time yourself on it.
Deliverable: One timed worked example in Programming.
03Work Advanced-level technical questions
- Spend the session on Advanced-level technical questions, which Mercy candidates report being tested on.
- Write one worked example in Advanced-level technical questions and time yourself on it.
Deliverable: One timed worked example in Advanced-level technical questions.
04Work Query-based problem solving
- Spend the session on Query-based problem solving, which Mercy candidates report being tested on.
- Write one worked example in Query-based problem solving and time yourself on it.
Deliverable: One timed worked example in Query-based problem solving.
05Answer out loud: Technical / Domain Questions
- Answer aloud, timed: Describe your experience with [specific programming language or technology].
- Answer aloud, timed: How do you approach debugging a complex software issue?
Deliverable: Spoken answers to 2 reported Technical / Domain Questions question(s), under time.
06Answer out loud: System Design / Architecture
- Answer aloud, timed: How would you design a system for [specific application, e.g., a patient scheduling system]?
- Answer aloud, timed: Describe the considerations you would take into account when architecting a cloud-based application.
Deliverable: Spoken answers to 2 reported System Design / Architecture question(s), under time.
07Answer out loud: Behavioral / Leadership
- Answer aloud, timed: Describe a time when you had to work with a difficult team member. How did you handle the situation?
- Answer aloud, timed: Give an example of a project where you took the lead. What was the outcome?
Deliverable: Spoken answers to 2 reported Behavioral / Leadership question(s), under time.
Expand any day for tasks and deliverables. Your progress is saved on this device.
Behavioural rounds judge the decision you made and what it cost.
Describe your experience with [specific programming language or technology].
Describe your experience with [specific programming language or technology].
Approach
- Pick a story where you made the decision, not one where you watched it.
- State the situation in two sentences and spend the rest on the reasoning.
- Give the blast radius: what could have broken, and what you measured.
- 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 difficult team member. How did you handle the situation?
Describe a time when you had to work with a difficult team member. How did you handle the situation?
Approach
- Pick a story where you made the decision, not one where you watched it.
- State the situation in two sentences and spend the rest on the reasoning.
- Give the blast radius: what could have broken, and what you measured.
- 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?
Give an example of a project where you took the lead. What was the outcome?
Give an example of a project where you took the lead. What was the outcome?
Approach
- Pick a story where you made the decision, not one where you watched it.
- State the situation in two sentences and spend the rest on the reasoning.
- Give the blast radius: what could have broken, and what you measured.
- 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 tasks when faced with multiple deadlines?
How do you prioritize tasks when faced with multiple deadlines?
Approach
- Pick a story where you made the decision, not one where you watched it.
- State the situation in two sentences and spend the rest on the reasoning.
- Give the blast radius: what could have broken, and what you measured.
- 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?
- 01
Describe your experience with [specific programming language or technology].
- 02
Describe a time when you had to work with a difficult team member. How did you handle the situation?
- 03
Give an example of a project where you took the lead. What was the outcome?
- 04
How do you prioritize tasks when faced with multiple deadlines?
How difficult are the interviews at Mercy, and how much preparation time should I expect?
The interviews can range in difficulty, but candidates typically report a rigorous process that includes both technical and behavioral assessments. Depending on your background, you should allocate several weeks to prepare thoroughly for the coding challenges and system design questions.
Mercy Software Engineer candidate reports ↗What differentiates successful candidates at Mercy?
Successful candidates demonstrate a strong alignment with Mercy's values, a solid technical foundation, and the ability to work collaboratively. Interviewers appreciate candidates who can communicate their thought process clearly and show enthusiasm for the role.
Mercy Software Engineer candidate reports ↗What is the culture and working style like at Mercy?
Mercy fosters a collaborative and patient-focused culture. You will find that teamwork and open communication are emphasized, creating an environment where innovative ideas are welcomed and valued.
Mercy Software Engineer candidate reports ↗What is the typical timeline from initial screen to offer?
The process can take anywhere from a few weeks to over a month, depending on scheduling and the number of interview stages. Candidates are encouraged to remain patient and proactive in following up.
Mercy Software Engineer candidate reports ↗Are there remote work or hybrid expectations for this role?
While specific arrangements may vary, Mercy has increasingly embraced flexible work options. Candidates should inquire about location expectations during the interview process.
Mercy Software Engineer candidate reports ↗What topics does Mercy test in interviews?
Mercy interviews most often cover Requirements Gathering, Structured Interviewing, Project Management, Decision Support Systems, and Business Analysis. The exact emphasis depends on the specific role you apply for.
Mercy Software Engineer candidate reports ↗Sources & methodology 3 sources ↗
No official company page is cited. Rounds and questions come from candidate reports and PracHub editorial material; each source shows the date it was read.
- 01Mercy Software Engineer candidate reports ↗
Company-reported rounds, questions and FAQ.
Candidate reports · Accessed 2026-09-22 - 02PracHub Software Engineer practice ↗
PracHub practice material, not company-reported.
PracHub page · Accessed 2026-09-22 - 03PracHub preparation framework ↗
PracHub preparation guidance.
PracHub page · Accessed 2026-09-22
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