SaaS & MVP Development

Custom web apps that replace the spreadsheets running your business

2 days ago

Back-End Development
Database Design
Front-End Development
Testing & QA
System Architecture
Full-Stack Development
API Design

Custom web apps that replace the spreadsheets running your business cover

Overview

Somewhere in your business there's a spreadsheet holding everything together. Or a tool you pay for that does 60% of what you need. Or an idea that won't leave you alone. That's where a custom web app comes in. I build web applications that fit the way your business actually works, instead of bending your business around someone else's software. What you get: • Discovery and scoping: we define what to build, and what not to • UX/UI design in Figma before a line of code is written • Development on proven stacks: Laravel, Node.js, React, MySQL, MongoDB • Integrations with your existing tools, APIs and AI (OpenAI, Claude) • Deployment on AWS, DigitalOcean or Cloudflare, plus ongoing support Recent example: a Laravel website plus an AI-powered browser extension for an AI writing product. Why me: 5+ years, 200+ US & EU brands, 4.9 rating. Projects start from $10,000 + VAT. You get a free estimate first, so there are no surprises. Tell me what's breaking (or what you're dreaming of). I'll tell you straight if it's worth building.

Deliverables

Discovery and scoping document with a clear feature list
UX/UI design in Figma, approved before development
Full-stack web application built and tested
Integrations with your tools, APIs and AI services
Deployment to production hosting
Handover, documentation and post-launch support

How it works

Free call: you walk me through the problem, I tell you if software is the answer
Scoping and fixed estimate, so cost and timeline are clear upfront
Design in Figma, then build in milestones you can test as we go
Launch, monitor and improve with you after go-live

FAQ

What does a custom web app cost?

Projects start from $10,000 + VAT. You get a free, detailed estimate after scoping, before you commit.

Can it connect to the tools we already use?

Do I need a full spec before we talk?

About the seller

Mantas Karmaza

€100M+ added via 4,000+ A/B tests for 360Cycles, Draco and over 200 other DTC brands

Lithuania

Most e-commerce sites bleed revenue. I plug the leaks, so the traffic you already pay for turns into orders. 10+ years in e-commerce growth, from RRR.lt to Flatyz.com and CCS Baltic. Founder of Mantas Digital (Vilnius, 2021). The numbers: • 4,000+ A/B tests run, €100M+ in extra revenue for clients across the US & EU • 200+ DTC brands helped • 400+ visual CRO audits delivered in 2026 • 4.9 rating across Clutch, Google, Trustpilot & Facebook (50+ verified reviews) Recent results: • 360 Degrees Cycles: €1.5M+ in sales on €30k+ invested • MeriWoolArt: +42% conversions • Draco Slides: +23% conversions, +265% mobile speed • Waterpik: 22% more orders What I do: CRO & UX audits, A/B testing, Shopify, WooCommerce & WordPress builds, speed, SEO, email & business automation, AI integration. If you want pretty, hire a designer. If you want profit, message me. Case studies: mantasdigital.com/case-studies

Member since2026

View Mantas's profile

More from Mantas

10% more conversions in 60 days, same traffic, or your money back Website care so your site never breaks the day your sales spike SEO that brings buyers ready to pay, not just pretty traffic graphs Find out exactly why visitors leave without buying, and fix it

From$10,000/project

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