Investigate a performance problem
A fixed-scope diagnostic of one slow, locking or expensive workload: written findings, prioritised next steps and a handover to your engineers.
Independent MySQL, MariaDB & Aurora MySQL consulting
Understand your database bottleneck. Leave with a clear plan.
Specialist performance investigations for software teams and agencies. Work directly with Krzysztof Książek on slow queries, recurring locking problems, and unexplained database latency—with clear findings and a prioritised plan for your engineers.
Fixed scope. Scheduled delivery. No ongoing support contract required.
Planning a new setup instead? See architecture design, review and build for MySQL, MariaDB, Aurora MySQL and ClickHouse.
Illustrative sample
Slow order history in a multi-tenant application
Why does the order-history page become slow for some tenants, and what should the team test first?
- No index matches the filter and sort together
- Deep pages use OFFSET
Estimate the large-tenant plan with EXPLAIN FORMAT=JSON before any EXPLAIN ANALYZE.
Synthetic MySQL scenario; no customer data or measured results.
Read the MySQL sample →Two ways to start
Investigate a problem, or design the system
Design, review or build a database architecture
Topology, failover and growth, planned with your team before the choices are hard to undo. You get a written design, and a separately scoped build if you want one.
From real audits
Anonymised write-ups of customer engagements, with the evidence each one used.
- Why a Galera cluster was slower than staging for an online shop
- A MySQL server that spent half its time waiting for locks
- A Galera cluster that became unstable when it was stretched to a second data centre
- A CPU-saturated MySQL server: full scans, long procedures and idle transactions
Who does the work
You work directly with the specialist.
DB-Ex is an independent database consultancy led by Krzysztof Książek. I handle the scoping, investigation, written findings, and technical handover personally.
Production database experience
Database reliability engineer on a large Amazon Aurora fleet since April 2025, including major version upgrades and schema and query work with development teams. Before that, MySQL operations and performance reviews as an operational DBA (2012–2015).
Career summary →Technical work you can inspect
Explore selected database articles and see how I structure an investigation — from evidence and uncertainty to recommended next steps.
- MySQL backup lab, part 9 – the harness that records evidenceHow a lab records its own evidence and stops on failure instead of reporting a green result.
- Galera Cluster – Understanding the network latency impactA latency experiment with its method and limits stated up front.
Support leadership and technical communication
Head of Support at Severalnines (2019–2025) after four years as a senior support engineer: complex customer escalations on MySQL and MariaDB, technical guides and webinars, and a Percona Live Europe talk on MySQL load balancers.
Where a focused investigation helps
Three common starting points
Queries are slow, but the cause is unclear.
A focused investigation helps establish what the evidence supports before choosing the next change.
How the diagnostic works →Your team needs an independent review before making a database change.
Clarify the assumptions, risks, and validation steps around a defined performance question.
What the review covers →A client project needs deeper MySQL expertise.
Bring a specialist into the investigation while your team retains delivery ownership.
Working with agencies →
The main offer
MySQL & Aurora Performance Diagnostic
A focused investigation of your database problem. Written findings, prioritised next steps, and a technical handover to your team.
What you receive
- Findings with their supporting evidence
- Prioritised recommendations
- A plan for validating changes
- Technical handover to your team
One environment and one principal question, with the scope, fee, and schedule agreed before work begins. Fixed fee, agreed after a short scope review.
How it runs
- Scope
- Evidence review
- Findings and recommendations
- Handover
For agencies and consultancies
Specialist database help for your client projects
When a client's MySQL problem needs a deeper investigation, bring in focused expertise without expanding your permanent team.
You retain the client relationship and implementation work. I provide the database investigation, written findings, and handover to your technical team.
Selected proof and technical writing
See how I approach database problems
- RecoveryLab
MySQL – test your backup by restoring it as a replica
A successful backup job does not prove you can recover. This lab restores a backup as a replica and records the evidence for each scenario.
- Architecture
MySQL Architecture – What to use? MySQL replication or Galera Cluster?
Asynchronous replication or Galera Cluster, compared across one, two and three data centres: failover, split-brain risk and the cost of network latency.
- Performance Illustrative
Sample MySQL diagnostic: slow order history in a multi-tenant application
The full structure of a diagnostic report: evidence with its provenance, findings separated from hypotheses, missing evidence, and validation steps.
Have a database question worth investigating?
Describe the system, the problem, and what you need to find out. We can then establish whether a focused engagement is the right next step.