RentSpree Software Engineer
Interview Guide

How does garbage collection work in your primary programming language?

Refactor a poorly structured, synchronous code block into an asynchronous, non-blocking implementation while ensuring thread safety.

A day of job_run history yields about 50,000,000 attempt records: (job_run_id, job_type, attempt, started_at, finished_at which is NULL when the worker died, lease_expires_at). Leases expire on a clock, so a job that outran its lease ran twice. Produce (a) every job_run_id whose attempts overlapped in wall-clock time and (b) the peak number of simultaneously running attempts per job_type with the minute it occurred. Target O(n log n). State how you treat a NULL finished_at and what clock skew does to your answer.

A tenant on the standard plan may hold at most 50 resources with status='active'. The create handler runs SELECT count(*) FROM resource WHERE tenant_id = $1 AND status = 'active', compares to 50, then inserts. Two creates arrive 3 ms apart on different instances and the tenant lands at 51. Name the anomaly, say whether PostgreSQL 16 READ COMMITTED or REPEATABLE READ prevents it and why, then give an implementation that holds the cap at READ COMMITTED with the exact statements. Finally, say what changes when the cap is 'at most one running export per tenant' on job_run.

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.

Explain the difference between object-oriented programming (OOP) and functional programming, and when you would choose one over the other.

What are the SOLID design principles, and how do they contribute to writeable, maintainable code?

What is the difference between relational and non-relational databases, and how do you decide which to use for a high-security financial transaction system?

Explain the concept of dependency injection and how it aids in unit testing.

Design and implement a robust utility function to parse and validate complex nested JSON payloads from a third-party credit bureau API.

Write a clean, self-contained service that aggregates data from multiple internal endpoints, handles partial failures gracefully, and returns a unified response.

Implement a rate-limiting mechanism for an API endpoint using an in-memory data store.

How would you design a highly secure and compliant tenant screening workflow that processes sensitive background checks?

Describe how you would transition a monolithic rental application platform into a microservices architecture without causing downtime.

How do you design a reliable event-driven system to handle real-time rent payment notifications using message brokers?

What strategies would you employ to cache database queries for frequently accessed rental listings while ensuring data consistency?

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.