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You will get fixed website performance issues hurting your conversions
Top Rated
Project details
Is your website's user experience hindering conversions due to slow loading times or inconsistent global delivery? This project eliminates UX-to-revenue friction by optimizing performance and ensuring lightning-fast global font and script delivery. Many businesses lose customers due to poor Core Web Vitals and suboptimal content delivery for international audiences. Our process audits your site's performance, identifies bottlenecks in font/script loading, and implements advanced caching and CDN strategies. We analyze your global audience and configure a robust delivery mechanism for a consistent, blazing-fast experience everywhere. The business ROI is clear: increased conversion rates, lower bounce rates, improved SEO rankings, and a superior user experience that translates directly into higher revenue.
Programming Languages
HTML & CSS, JavaScript, TypeScriptCoding Expertise
Cross Browser & Device Compatibility, Performance Optimization, DesignWhat's included
| Service Tiers |
Starter
$300
|
Standard
$495
|
Advanced
$750
|
|---|---|---|---|
| Delivery Time | 3 days | 5 days | 7 days |
Number of Revisions | 0 | 0 | 0 |
Bug Investigation | |||
Fix Documentation | |||
Detailed Code Comments |
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Fast Delivery
+$100 - $150Frequently asked questions
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GB
Goran B.
Oct 7, 2025
UpWork API Key Specialist
AO
Alex O.
Jun 23, 2025
Bubble Developer for Hotel Booking Flow (using booking API)
David helped integrate a complex API into our Bubble platform and he was fantastic to work with. Always quick to respond, he went above and beyond to build custom code solutions that really fit our needs. Super reliable, knowledgeable, and easy to communicate with - we really enjoyed working with him and would definitely recommend him for any API or Bubble-related work.
PC
Piers C.
Jun 16, 2025
Bubble.io / Python - Need to send data to a python script and return the result to bubble
Great work
EC
EL Mahdi C.
May 13, 2025
Automate Q&As Flashcards
Great as always
SW
Swetlana W.
Apr 28, 2025
Fix push notification in firebase.
I have been working with David for a long time. Every task has been implemented superbly so far. I can recommend him!
About David
API Integration Specialist | System Architect | Backend Developer
100%
Job Success
London, United Kingdom - 2:41 am local time
Having scaled integrations inside Mastercard and Vodafone, I've seen exactly where systems snap under sudden volume. My solutions don't just rely on theoretical system architecture—they are built on hands-on delivery experience that keeps infrastructure ahead of growth.
Who I am
✮ Expert-Vetted — Top 1% on Upwork
✮ Reliably committed for 11+ years to delivering solutions for large corporations like Mastercard & Vodafone.
✮ Experience working in large client facing consultancy
✮ Experienced solving enterprise-grade backend problems
✮ Integrated 50+ POS systems to enable accurate demand forecasting
✮ Data Driven decision making
✮ 100% customer satisfaction guarantee
What I Bring
• Deep Java + API architecture specialization, focusing on iPaaS and complex system integrations.
• Ability to reverse-engineer and debug brittle legacy systems others avoid.
• API security, management, automation, and observability built in from the start.
• Honest scope-setting—I tell you exactly what's needed, what it costs, and challenge the standard approach when a better one exists.
• I lead initiative, track delivery velocity (not just hours logged), and focus on delivered value over completed tickets.
• Long-Term Focus: Built for embedded team collaboration and multi-year partnerships.
How I use AI
I openly leverage AI strictly as an efficiency tool to deepen accuracy, build relevant content, accelerate code delivery, and map systems quickly—never to replace the authentic strategy, human insight, and problem-solving drawn from my computer science background and years of field experience. From my experience this has led to protecting my customers investment, optimized costs and an increase in overall customer satisfaction.
Let's talk:
Message me directly or send a job invite — happy to hop on a call and walk through your setup.
Steps for completing your project
After purchasing the project, send requirements so David can start the project.
Delivery time starts when David receives requirements from you.
David works on your project following the steps below.
Revisions may occur after the delivery date.
Performance Audit
Identify loading bottlenecks and UX pain points.
Strategy Design
Create an optimized delivery plan using CDN and caching.