Tame Lock Contention on a Shared Property-Manager CRM Database
Overview
What this challenge is about.
Identify and fix eight blocking hotspots in a CRM database using SKIP LOCKED and READ COMMITTED. Validate with a traffic replay. Earn a verifiable certificate.
The scenario
Helmstadt builds a vertical customer-relationship product for residential property managers and runs every one of its 4,800 customer companies on one shared PostgreSQL 16 transaction-processing database. Six oversized customers concentrate enough simultaneous write traffic to stall everyone else, making lock contention a whole-fleet reliability problem rather than a single customer's issue.
The Brief
What you'll do, and what you'll demonstrate.
Find and fix the lock contention degrading shared-database response times for all 4,800 customers, and prove the gain on a recorded one-hour traffic replay.
Earning criteria — what you'll demonstrate
- Read pg_locks and pg_stat_activity evidence to locate and rank real blocking hotspots.
- Match each contention mechanism to a correct, safe concurrency-control fix.
- Apply SELECT ... FOR UPDATE SKIP LOCKED so worker queues drain without head-of-line blocking.
- Choose isolation levels deliberately and reason about where advisory locks are safe substitutes.
- Validate database changes with a recorded-workload replay and defend the result with numbers.
Program Fit
Where this fits in your program.
Sharpens the same skills your degree expects you to demonstrate.
Aligned coursework coming soon.
Skills
Skills you'll demonstrate.
Each one shows up on your verified credential.
- Concurrency Control
Apply concurrency control to solve real industry problems and demonstrate production-level capability.
- Lock Contention
Apply lock contention to solve real industry problems and demonstrate production-level capability.
- Postgresql
Apply postgresql to solve real industry problems and demonstrate production-level capability.
- Isolation Levels
Apply isolation levels to solve real industry problems and demonstrate production-level capability.
- Skip Locked
Apply skip locked to solve real industry problems and demonstrate production-level capability.
- Workload Replay
Apply workload replay to solve real industry problems and demonstrate production-level capability.
Careers
Career paths this challenge builds toward
Completing this challenge demonstrates skills that transfer directly to these roles:
Database Reliability Engineer
Reliability engineers keep shared databases fast under multi-customer load. This challenge mirrors that work end to end: you diagnose blocking from live lock evidence, ship safe concurrency fixes, and prove the reliability gain with a recorded replay rather than a guess.
This challenge sharpens
- lock-contention
- concurrency-control
- workload-replay
Senior PostgreSQL Administrator
Senior PostgreSQL administrators tune isolation and locking for high-traffic systems. Here you practice exactly that, choosing isolation levels deliberately and applying SKIP LOCKED to worker queues on a realistic PostgreSQL 16 workload.
This challenge sharpens
- postgresql
- isolation-levels
- skip-locked
Backend Performance Engineer
Performance engineers turn tail-latency problems into measured wins. This challenge builds that muscle: you trace 99th-percentile slowdowns to lock contention, redesign the access patterns, and defend the improvement with replay numbers.
This challenge sharpens
- lock-contention
- concurrency-control
- workload-replay