As a Software Engineer at Waystar, you will play a pivotal role in developing and scaling the cloud-based SaaS technology that simplifies the complex world of healthcare payments. Waystar operates at the intersection of healthcare and financial technology, processing billions of transactions annually for healthcare providers of all sizes. The software you build and optimize directly impacts how hospitals, clinics, and practices manage their revenue cycles, ensuring they can focus on what matters most: patient care. You will join a collaborative engineering team focused on high-throughput data processing, robust application security, and intuitive user interfaces. The technical challenges here involve handling massive datasets, maintaining high system availability, and implementing complex business logic to navigate the shifting landscape of healthcare regulations. Whether you are working on core backend services, optimizing relational databases, or building modern frontend workflows, your contributions will drive efficiency and transparency across the entire healthcare ecosystem. This role is ideal for engineers who thrive on solving practical, real-world problems. Rather than focusing on abstract algorithmic puzzles, values clean code, system reliability, and database efficiency. It is a highly collaborative environment where your technical decisions have immediate, visible impacts on the financial health of healthcare organizations nationwide. Waystar
Initial Touchpoint
reportedIncludes an online pre-screening test or a technical screening call with a recruiter focusing on foundational computer science concepts.
What to demonstrate
- Includes an online pre-screening test or a technical screening call with a recruiter focusing on foundational computer science concepts
- Depth in SQL (querying & answering SQL questions)
How to prepare
- Answer aloud and timed: Write a function to reverse a string in place, and discuss how you would optimize it for memory efficiency.
- Answer aloud and timed: Given an array of integers, find the first non-repeating element.
Technical Round
reportedInvolves code pairing on algorithm challenges and a dedicated database and SQL evaluation.
What to demonstrate
- Involves code pairing on algorithm challenges and a dedicated database and SQL evaluation
- Depth in SQL (querying & answering SQL questions)
How to prepare
- Answer aloud and timed: Implement a basic algorithm to detect if a given string is a palindrome, ignoring spaces and capitalization.
- Answer aloud and timed: How would you find the duplicate elements in a list while maintaining a runtime complexity of O(n)?
Meet Hiring Managers
reportedDiscussion with hiring managers and potentially senior leadership about your career background and system design experience.
What to demonstrate
- Discussion with hiring managers and potentially senior leadership about your career background and system design experience
- Depth in SQL (querying & answering SQL questions)
How to prepare
- Prepare two projects you led end to end, each with the decision you owned and what it cost.
- Have three questions about the team's roadmap and how success is measured in the first six months.
PracHub editorial advice for the preparation topics above.
Focus on the fundamentals
Prioritize clean code, proper variable naming, and basic data structures over complex algorithmic tricks.
Practice your SQL
Do not neglect the database portion of the preparation. Being able to write accurate queries quickly is a major differentiator.
Communicate your thought process
Keep your interviewers engaged by explaining your logic, discussing potential trade-offs, and asking clarifying questions before you begin coding.
Choose a category, try a prompt, then open its approach, worked solution or follow-up when you need it.
Write a function to reverse a string in place, and discuss how you would optimize it for memory efficiency.
Write a function to reverse a string in place, and discuss how you would optimize it for memory efficiency.
Approach
- Say what the runtime actually does before reasoning about the code.
- Name what is shared across threads and what owns each piece of state.
- Identify the window where an invariant is briefly untrue.
- 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?
Given an array of integers, find the first non-repeating element.
Given an array of integers, find the first non-repeating element.
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?
Implement a basic algorithm to detect if a given string is a palindrome, ignoring spaces and capitalization.
Implement a basic algorithm to detect if a given string is a palindrome, ignoring spaces and capitalization.
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?
How would you find the duplicate elements in a list while maintaining a runtime complexity of O(n)?
How would you find the duplicate elements in a list while maintaining a runtime complexity of O(n)?
Approach
- Say what the runtime actually does before reasoning about the code.
- Name what is shared across threads and what owns each piece of state.
- Identify the window where an invariant is briefly untrue.
- 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?
Write a SQL query to find the second-highest salary from an employee table.
Write a SQL query to find the second-highest salary from an employee table.
Approach
- Name the grain you start from and join outward from it.
- Check whether any join is one-to-many before aggregating, or the sums inflate.
- Say which index the query would use, and what makes it unusable.
- 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?
Given two tables, `Orders` and `Customers`, write a query using an inner join to list all orders along with cu
Given two tables, Orders and Customers, write a query using an inner join to list all orders along with customer names.
Approach
- Name the grain you start from and join outward from it.
- Check whether any join is one-to-many before aggregating, or the sums inflate.
- Say which index the query would use, and what makes it unusable.
- 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?
Explain the difference between `GROUP BY` and `ORDER BY` in SQL, and write a query demonstrating both.
Explain the difference between GROUP BY and ORDER BY in SQL, and write a query demonstrating both.
Approach
- Name the grain you start from and join outward from it.
- Check whether any join is one-to-many before aggregating, or the sums inflate.
- Say which index the query would use, and what makes it unusable.
- 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?
How do you optimize a slow-running SQL query? Describe your approach to indexing.
How do you optimize a slow-running SQL query? Describe your approach to indexing.
Approach
- Name the grain you start from and join outward from it.
- Check whether any join is one-to-many before aggregating, or the sums inflate.
- Say which index the query would use, and what makes it unusable.
- 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?
Convert the listing endpoint from offset pages to stable cursors
GET /v1/resources returns a tenant's resources newest-updated first, today with page and per_page, backed by index (tenant_id, status, updated_at DESC, resource_id DESC). Callers are a browser feed and a nightly sync job that walks every page. Users report items appearing twice or vanishing between pages, and page 400 is slow. Design the cursor contract: what the cursor contains and how it is encoded, the exact WHERE and ORDER BY, what happens when a row's updated_at changes mid-walk, how a client detects the end, and what the sync job does when a cursor is rejected.
Approach
- Separate the two defects, because they have different fixes. Cost: OFFSET n makes the engine produce and discard n rows, so price grows with page depth rather than page size and page 400 pays for 400 pages of work. Correctness: while the set shifts, rows cross the offset boundary and are skipped or repeated, and nothing in the response lets the client detect it.
- Write the seek: WHERE tenant_id = $1 AND status = $2 AND (updated_at, resource_id) < ($k, $id) ORDER BY updated_at DESC, resource_id DESC LIMIT n. The tie-break is not decoration - updated_at is not unique, and two rows sharing a timestamp across a page boundary reintroduce exactly the skip this was adopted to remove. PostgreSQL seeks the composite index on the row-value comparison directly; on an engine that does not optimise a row constructor, expand it into the equivalent OR form or the plan quietly degrades to a scan.
- Encode the cursor as an opaque token carrying the sort key, the id, and a fingerprint of the filter and sort order, signed or at minimum validated. A cursor replayed against a different sort or filter must be a 400 with its own code, not a silently wrong page - the sync job cannot notice the difference otherwise.
- State the guarantee precisely rather than generously. Keyset is stable against inserts and deletes elsewhere in the set, because the position is a value and not a count. It is not a snapshot: updated_at is mutable, so a row that is edited during the walk re-sorts and may be seen twice or not at all. If the sync job needs exactly-once coverage, order on an immutable key such as (created_at, resource_id), or walk resource_revision by revision_id and treat updated_at as data.
Follow-up
- The client wants a total count and the ability to jump to page 400. What can you honestly offer instead, and what does each option cost?
- How do you paginate backwards, and what does that require of the index?
Make the resource write endpoint safe for retrying clients
The edge API accepts POST /v1/resources at 1.2k writes/second peak under a 400 ms p99 budget, and clients retry on timeout. idempotency_key has PRIMARY KEY (tenant_id, idempotency_key) plus request_fingerprint CHAR(64), state in ('in_flight','succeeded','failed'), response_status, response_body, resource_id, locked_until and expires_at. Specify the exact sequence the handler runs: what the second request does when it arrives while the first is still executing, what a retry carrying a different body receives, what happens when a process dies mid-request, and how the table is kept from growing without bound.
Approach
- Start from the race rather than the happy path. Insert the key row first, in its own short transaction, with state 'in_flight' and locked_until set to now() plus the request deadline. The unique constraint on (tenant_id, idempotency_key) is the arbitration mechanism: exactly one caller commits the insert, and every other caller takes a unique violation (SQLSTATE 23505) and becomes a follower. Reading the table and then inserting is a check-then-act race that both callers pass, and they pass it most often under the load that generates the retries.
- Give the follower a branch for every state it can observe, with no fall-through to doing the work: fingerprint mismatch means the key is being reused for a different request, so reject with 422 and never replay the stored response; 'succeeded' replays response_status and response_body verbatim; 'failed' allows a fresh attempt; 'in_flight' with locked_until in the future is answered with 409 and a retry hint, or a short bounded wait, because the only alternative is executing the effect twice.
- Commit the effect and the record of the effect together. The resource insert, its resource_revision row, its outbox_event row and the transition of the key row to 'succeeded' all happen in one transaction, so no crash can leave the work done and the key still 'in_flight'. The earlier insert is deliberately a separate transaction: it has to be visible to a concurrent caller before the work starts, which an uncommitted row is not.
- Close the wedged-key path. A process that dies after the insert leaves a row that would otherwise block that key forever, which is what locked_until exists for. Reclaim with a single conditional statement, UPDATE ... SET state='in_flight', locked_until=now()+interval WHERE ... AND state='in_flight' AND locked_until < now(), and treat a zero rowcount as losing the reclaim. Two statements that read and then update reintroduce the original race one layer down.
Follow-up
- The stored response body averages 200 KB and this table is now the largest in the database. What do you store instead, and what does a replay return once the body has been pruned?
- A client library generates a fresh idempotency key on every attempt. What breaks, which layer should have caught it, and does the server have any defence?
Every query on one table stalls for forty seconds mid-deploy
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
- 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.
- 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.
- 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.
- 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?
Built from the rounds and topics Waystar candidates report.
Prepare, practise & reflect
One practical outcome each day. Spend longer where you need it.
0 / 7 done01Map the Waystar loop
- Write out the reported sequence: Initial Touchpoint, Technical Round, Meet Hiring Managers.
- 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 SQL (querying & answering SQL questions)
- Spend the session on SQL (querying & answering SQL questions), which Waystar candidates report being tested on.
- Write one worked example in SQL (querying & answering SQL questions) and time yourself on it.
Deliverable: One timed worked example in SQL (querying & answering SQL questions).
03Work Behavioral interview (work style & fit)
- Spend the session on Behavioral interview (work style & fit), which Waystar candidates report being tested on.
- Write one worked example in Behavioral interview (work style & fit) and time yourself on it.
Deliverable: One timed worked example in Behavioral interview (work style & fit).
04Work Data Structures & Algorithms (DSA)
- Spend the session on Data Structures & Algorithms (DSA), which Waystar candidates report being tested on.
- Write one worked example in Data Structures & Algorithms (DSA) and time yourself on it.
Deliverable: One timed worked example in Data Structures & Algorithms (DSA).
05Answer out loud: Coding & Algorithmic Problem Solving
- Answer aloud, timed: Write a function to reverse a string in place, and discuss how you would optimize it for memory efficiency.
- Answer aloud, timed: Given an array of integers, find the first non-repeating element.
Deliverable: Spoken answers to 2 reported Coding & Algorithmic Problem Solving question(s), under time.
06Answer out loud: Database & SQL Queries
- Answer aloud, timed: Write a SQL query to find the second-highest salary from an employee table.
- Answer aloud, timed: Given two tables, `Orders` and `Customers`, write a query using an inner join to list all orders along with customer names.
Deliverable: Spoken answers to 2 reported Database & SQL Queries question(s), under time.
07Answer out loud: Behavioral & Cultural Fit
- Answer aloud, timed: Why do you want to work for Waystar, and how does your background align with our mission?
- Answer aloud, timed: Tell me about yourself and walk me through a significant technical project you recently completed.
Deliverable: Spoken answers to 2 reported Behavioral & Cultural Fit 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.
Why do you want to work for Waystar, and how does your background align with our mission?
Why do you want to work for Waystar, and how does your background align with our mission?
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?
Tell me about yourself and walk me through a significant technical project you recently completed.
Tell me about yourself and walk me through a significant technical project you recently completed.
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 on a legacy codebase or migrate data. How did you handle the challenges?
Describe a time when you had to work on a legacy codebase or migrate data. How did you handle the challenges?
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?
Tell me about a time you disagreed with a team member or manager on a technical approach. How did you resolve
Tell me about a time you disagreed with a team member or manager on a technical approach. How did you resolve it?
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
Why do you want to work for Waystar, and how does your background align with our mission?
- 02
Tell me about yourself and walk me through a significant technical project you recently completed.
- 03
Describe a time when you had to work on a legacy codebase or migrate data. How did you handle the challenges?
- 04
Tell me about a time you disagreed with a team member or manager on a technical approach. How did you resolve it?
What is the difficulty level of the technical interviews at Waystar?
The technical interviews generally focus on fundamental engineering skills and are typically rated as easy to average in difficulty. You will not face highly abstract, competitive-programming-style questions. Instead, expect practical coding tasks and SQL queries that mirror real-world development challenges.
Waystar Software Engineer candidate reports ↗Where are the Software Engineer positions located?
Many of Waystar's engineering teams are centered around major office hubs, particularly in Atlanta, GA and Chicago, IL. Depending on the specific team and role, there may be hybrid work arrangements available.
Waystar Software Engineer candidate reports ↗How should I prepare for the SQL portion of the interview?
Ensure you are highly comfortable with database joins, aggregations, subqueries, and basic database design principles. Reviewing common SQL query patterns and practicing data extraction tasks will prepare you well for this part of the evaluation.
Waystar Software Engineer candidate reports ↗What is the typical timeline for the hiring process?
The process is designed to be efficient, often wrapping up within a few weeks. However, coordination times can vary depending on the team's schedule, so maintaining proactive communication with your recruiter is highly recommended.
Waystar Software Engineer candidate reports ↗What topics does Waystar test in interviews?
Waystar interviews most often cover Stakeholder Management, Stakeholder Communication, Presentation Skills, Problem Solving, and Requirements Gathering. The exact emphasis depends on the specific role you apply for.
Waystar 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.
- 01Waystar 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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