I Don't Advise on Core Web Vitals.
I Fix Them.
I join your engineering team for 1 to 2 sprints. I fix the root architecture. I train your developers to keep it fast. You keep the results. Permanently.
Book a Free Strategy CallSee How I WorkTrusted by market leaders
Slow by Mistake. Slow by Design.
Every slow website has two types of problems. "Slow by mistake" means something went wrong along the way. An unoptimized image, a render blocking script, a misconfigured CDN. I fix those first because they deliver immediate results.
"Slow by design" is harder. Strategic choices that affect performance at a deeper level. A heavy JavaScript framework. A third party tag manager loading 40 scripts. A hydration strategy that blocks the main thread. Fixing these requires understanding why the choices were made and engineering better alternatives that preserve the business logic.
Most consultants stop at "slow by mistake." I solve both.
Week 1: Diagnostic and Baseline
I deploy CoreDash, my proprietary RUM platform, to capture what your real users actually experience. While field data accumulates, I manually review your codebase. JavaScript execution patterns. Rendering pipelines. Third party dependencies. LoAF API attribution. By end of week one you have a complete map of every "slow by mistake" and "slow by design" issue on your site, prioritized by revenue impact.
Week 2 and 3: The Engineering Sprints
I embed with your development team. I refactor critical rendering paths. I implement Speculation Rules for instant navigations. I restructure third party loading sequences. Every fix is validated in real time against CoreDash field data, not Lighthouse. We do not wait 28 days for Google's CrUX report to know if something worked. We know within hours.
Week 4: Lock In and Handoff
I configure performance budgets in your CI/CD pipeline so regressions get blocked before they ship. I train your developers on RUM data interpretation and performance debugging. CoreDash stays active after I leave. Your team keeps the same monitoring I used to fix the site. That is what "permanent" means.


I fix the code. You keep the results.
Client Success
Don't just take my word for it
VP Product, Expedia Group
"We had 80+ third-party scripts and were failing CWV on every major property. Arjen got us passing without touching our ad revenue."
VP Engineering, People Inc
"Seven brands, seven different stacks. Every single one got faster. No compromises on what makes each property unique."
Head of Platform, Adevinta
"45% reduction in blocking time across 15 marketplaces. And we didn't lose a single ad placement."
Lead Developer, Alza
"Transferred knowledge to our engineering team. We can now diagnose and resolve performance issues independently."
Head of Engineering, Swift
"Layout shift on checkout eliminated entirely. Went from 0.4 to 0.02 CLS across mobile and desktop."
CTO, DPG Media
"He found bottlenecks in our component library that we'd missed for two years. Performance gains were visible within days."
Product Lead, Miro
"Our dashboards were choking on main-thread work. 25% reduction in CPU usage. Users noticed immediately."
Engineering Manager, Zalando
"Every other audit we've had gave us a list of problems. This one told us exactly what to fix first and why."
VP Engineering, Loop
"Mobile load time down 800ms. 7% lift in checkout conversion. The ROI justified the investment immediately."
Head of Digital, Rituals
"We used to break performance every other sprint. He set up budgets in our pipeline. Haven't had a regression since."
17 years. One specialty.
"I have fixed Core Web Vitals on sites with 900,000+ pages. Not with a PDF report. With code, monitoring, and fixes that lasted."
Proof, Not Promises
I do not measure success in Lighthouse scores. I measure it in revenue impact, search visibility, and Core Web Vitals that stay green after I leave. Here is what that looks like in practice.

Complex Platform Optimization
A major classified marketplace running millions of listings. Standard agency advice had failed to move the needle. I diagnosed rendering bottlenecks and third party governance issues that previous audits had missed entirely. The result: protected ad revenue and restored search visibility across their entire portfolio.

60 Minutes. Measurable Impact.
A focused diagnostic for a high traffic media publisher managing a complex ad stack. Within one session I identified the exact layout instability sources and LCP bottlenecks. Their team implemented the fixes the same week. Pages that were failing CWV moved to "Good" status, protecting their organic search traffic.

Ongoing Collaboration
When a leading Dutch digital agency needs performance engineering for their enterprise clients, they bring me in. Not as a subcontractor. As their specialist.
Who This Is For
This is not a quick fix service. It is a strategic engagement for organizations with engineering teams, production traffic, and a direct line between site speed and revenue.
Enterprise
E-Commerce
Your product pages load in 4+ seconds on mobile. Your checkout conversion is bleeding. Your agency ran Lighthouse and told you to "optimize images." You need someone who understands rendering pipelines, not just best practice checklists.
Complex SaaS
Applications
Your dashboard feels sluggish. Users report clicks that take a second to respond. Your React or Angular app has INP scores in the red and your team has no idea where to start. I profile the main thread and fix what's blocking it.
Digital
Publishers
Your ad ops team says you can't touch the tag manager. Your SEO team says Core Web Vitals are tanking your rankings. Everyone says it's impossible to have both. I have fixed this exact problem for multiple publishers. You keep the ads. You pass the vitals.
Looking for quick, targeted help instead? Check out my on-call consultancy for immediate solutions.
Ready to Fix This?
I take on a maximum of 3 strategic engagements per quarter. Each one gets my full, personal attention. No junior associates. No outsourced analysis. Just me, embedded with your team.
Full Consultancy starts at €15,000 for a defined sprint. The exact scope depends on your platform, your team, and how deep we need to go. Fixed scope, fixed timeline, fixed deliverables. For context: Loop Earplugs saw a 7% conversion lift from 800ms less load time. On a site doing €1M/month, that kind of improvement pays for the engagement in the first week.
Not ready for a full engagement? Book an on-call session at €150/hr. Get a specific problem solved and see how I work. Many of my largest clients started with a single 2-hour session.
The initial strategy call is 20 minutes and costs you nothing. I will review your current Core Web Vitals data and tell you honestly whether I can help. If I can't improve your numbers, I will tell you on the call.
No Obligation
The call is free. If I can't improve your numbers, I'll tell you.
No Disruption
I work inside your existing sprints, tools, and repo. No rewrites.
Fixed Scope
Defined timeline, defined deliverables, no open ended billing.
Straight Answers on Process, Investment, and Results
Investing in performance engineering is a strategic decision. You need to understand the return, the integration with your roadmap, and the technical depth of what gets delivered. These are the questions I hear most from engineering leads and decision makers.
Strategy, ROI and Business Impact
What is the expected ROI of a Core Web Vitals consultancy?
The return is measurable in user retention and conversion. High volume storefronts like Loop Earplugs saw a 7% conversion lift after reducing mobile load times by 800ms. Adevinta improved their overall Core Web Vitals metrics by 145% to protect ad revenue at scale. I validate every optimization against Real User Monitoring data from CoreDash to ensure the investment impacts your revenue immediately.
Who is this consultancy designed for?
I work with organizations where site speed is a primary business asset. Enterprise E-commerce that depends on conversion stability. Complex SaaS applications that need sub-200ms interaction latency for user trust. Digital Publishers balancing heavy ad stacks with the Core Web Vitals scores required for search visibility. If you operate at scale, technical performance is not optional.
Do you guarantee specific Core Web Vitals scores?
I guarantee the maximum performance possible within your technical constraints. My target is passing CrUX metrics at the 75th percentile across LCP, CLS, and INP. More importantly, I focus on the metrics that drive business outcomes. We prioritize fixes based on their impact on real users and revenue rather than synthetic scores.
Why do we need a specialist instead of our current agency?
Good agencies apply standard best practices. I engineer performance based on how browsers actually execute code. I diagnose complex bottlenecks that standard audits miss. Hydration mismatches in Next.js. Third party script governance on high traffic media sites. Layout instability caused by ad injection timing. I have forgotten more about PageSpeed than most SEO agencies will ever learn. We all have our specialty. They might patch some Core Web Vital issues. I fix them permanently.
Technical Scope and Stack Capabilities
What technology stacks do you support?
All major web architectures. I understand the deep mechanics of how browsers render pages. That knowledge applies whether you run Next.js, Nuxt, Magento, Salesforce Commerce Cloud, or a custom PHP stack. I handle complex environments including Single Page Applications, Server Side Rendering, static site generators, and heavy third party dependencies. In 17 years of performance consultancy, I have worked with almost every platform and every backend.
How do you handle Interaction to Next Paint (INP) issues?
INP optimization requires precise management of the main thread. I use the LoAF (Long Animation Frames) API for detailed attribution of what blocks interaction responsiveness. We profile input latency and processing times to implement yielding strategies, optimize event listeners, and restructure JavaScript execution to keep your application responsive under load.
Will we need to rewrite our entire frontend?
Complete rewrites are rarely necessary. I focus on surgical, high impact changes. Optimizing resource loading strategies. Restructuring rendering paths. Adjusting script timing. I often resolve site-wide failures by refactoring specific heavy components or adjusting hydration logic. Maximum impact with minimal code disruption.
How does CoreDash differ from our existing monitoring?
CoreDash is built specifically for Core Web Vitals optimization work. Unlike general purpose analytics tools, it provides full attribution for every metric. You see exactly which element, script, or resource caused each LCP, INP, or CLS event. It validates fixes in real time against actual user sessions instead of waiting 28 days for Google's CrUX report. And it tracks every URL on your site without artificial limits or data retention caps.
Workflow, Integration and Deliverables
How do you integrate with our engineering team?
I work directly within your existing infrastructure. I analyze the codebase to identify root causes and provide well documented tickets with code examples. I join your sprints. I participate in code reviews. I transfer knowledge to your developers through hands-on collaboration, not slide decks. My goal is to upskill your team so they maintain high performance independently.
What are the specific deliverables of a full engagement?
You receive a deep technical analysis, a prioritized roadmap, and direct engineering support. This includes implemented fixes for CWV metrics, performance budgets configured in your CI/CD pipeline, and a fully set up CoreDash monitoring dashboard. I deliver code, configuration changes, and documentation. Not a PDF report.
How do you prevent performance regressions?
We automate it. I implement performance budgets in your deployment pipeline. If a new feature introduces layout shifts or main thread blocking, the build flags it before it reaches production. CoreDash provides continuous monitoring with instant alerts. Your team catches regressions the day they happen, not 28 days later in Search Console.
What is the difference between an Audit and Full Consultancy?
An audit identifies the problems. Consultancy solves them. If your team is strong and just needs direction, an audit or short consult provides the roadmap. If you need an expert embedded in your codebase to make the deep technical changes and guide the implementation through to verified results, full consultancy is the right choice.
Results, Timelines and Ad Revenue
How quickly will we see improvements in our Core Web Vitals?
You will see changes in CoreDash immediately after deployment. We do not wait for the 28 day CrUX cycle. My process typically delivers measurable performance gains within the first sprint. We verify every fix against real user data in real time, allowing us to iterate fast and confirm results weeks before Google reports them.
Can we pass Core Web Vitals without removing our Ads or Analytics?
Yes. You do not need to choose between ad revenue and performance. I specialize in third party governance. We do not remove your tags. We change how and when they load. I implement strategies that meet ad viewability requirements without blocking the main thread or causing layout shifts. My publisher clients maintain their RPM while passing Core Web Vitals.
What do you need from us to get started?
Access to your staging environment, your repository (GitHub or GitLab), and your current analytics. I do not require weeks of onboarding meetings. Once I have access, I begin the deep technical analysis immediately. We typically go from signed agreement to first findings within 5 business days.