I build websites, systems, and apps
integrated with what your company already uses
From MVP to internal systems, connected to ERP, CRM, payments, and AI. 6+ years with .NET, specialized in Sankhya ERP.
How I can help
From websites to integrated systems. Focused on the problem you need solved, not jargon.
Custom development
Websites, web systems, and apps, from MVP to a full internal system. .NET backend, React or Angular frontend, React Native apps, CI/CD deploys.
Companies, startups, and foundersSystems integration
I connect ERP, CRM, payments, and supplier APIs. With queues and automatic retry when something fails.
Companies whose systems don't talk to each otherAI integration
I put AI where it solves a problem: chat support, data analysis, and process automation, connected to your systems.
Companies that want to use AI day to dayLegacy modernization
I migrate GeneXus, Windows Forms, and old systems to .NET and Angular, module by module.
Companies stuck with an old systemTeam reinforcement
I join your project, absorb the context, and deliver. No long ramp-up.
Overloaded teamsProjects and results
Systems running in production at companies, measured by what they changed in the operation.
Systems for companies
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~5 s per complex query, down from 10–20 s
Sales Force
New web and mobile sales app for 60+ sales reps, integrated with Sankhya ERP. PIX, card payments, ERP posting, and invoicing went from manual to automatic.
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8 queues in parallel, no order arriving before its customer
Sales ↔ CRM integration
Event-driven middleware that syncs orders, customers, contacts, and addresses between the sales platform and a CRM. I fixed the race condition between queues with ordered consumption and staggered retries, covered by integration tests.
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10+ modules migrated from GeneXus to .NET and Angular
Legacy migration
Sales, inventory, commissions, orders, reports, and sales portal, migrated module by module. Integrated with Sankhya ERP and supplier APIs.
My own products
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Conta na Mesa
Bill splitter for bars and restaurants. Reads the receipt and splits it per person.
- React
- .NET
- PostgreSQL
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Fucin
Pet health app. Vaccines, appointments, and medications with notifications. In closed beta.
- React Native
- .NET
- SQL Server
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Promolance
Deal finder with automated scraping and AI for price analysis and chat-based recommendations.
- React
- Node.js
- Python
- PostgreSQL
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Psitelos
Practice management for psychologists: calculates the ideal price per session and handles scheduling and finances.
- .NET
- React
- PostgreSQL
Who you'll be working with
I'm João Saraiva, a full-stack .NET developer. I spent the last years inside a solar energy distributor and a textile manufacturer. There I migrated GeneXus systems to .NET and Angular. I rewrote the sales app and integrated Sankhya ERP with a CRM over RabbitMQ. I also built the Azure CI/CD and ran the production server. I take on projects through SaraivaTech.
- 2019–2021
First systems: Windows Forms, SQL, and reports.
- 2021–2025
GeneXus to .NET and Angular migration and the new sales app, as an outsourced developer.
- 2025–2026
Sales-to-CRM integration over RabbitMQ, Azure CI/CD, and running the production server.
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I flag it before it's a problem
I estimate with realistic margins. If anything changes, you hear it before the deadline.
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I document what I do
Decisions, architecture, and lessons are written down. The next developer understands the code.
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I understand the business before coding
Sometimes the best solution is not to build.
How it works
Simple and transparent process, from first contact to delivery.
Initial conversation
I understand your project, scope, timeline and budget. No commitment.
Proposal
I send a detailed scope, timeline and pricing. Fully transparent.
Development
Short sprints with frequent deliveries. You follow every step.
Delivery + Support
Deployment, documentation and 30 days of included support.
Frequently asked questions
Common questions about working with me.
How does the commercial process work?
Free initial conversation to understand the project. Then I send a proposal with detailed scope, timeline, and investment. You only decide with everything on the table.
How much does it cost?
Fixed-scope projects start at R$ 6,000. Team reinforcement and consulting are billed hourly, from R$ 150. The exact price comes in the proposal, after the first conversation, with scope and timeline in writing.
Do you work with Sankhya?
Yes. I've integrated Sankhya with sales apps, CRM, payments (PIX and cards), and supplier APIs.
Do you work remotely?
Yes, 100% remote. Video calls at agreed times.
How long does a project take?
Simple MVP: 4-8 weeks. More complex systems: 2-4 months. It depends heavily on scope, but I always estimate with a realistic margin.
Do you work with contracts?
Yes. Simple contract with clear scope, timeline, and payment terms. No red tape.
What if I need changes later?
30 days of included support after delivery. For bigger adjustments, we scope a new agreement with fair terms.
Do you work with my specific tech stack?
Yes, I have experience with many technologies. I can adapt to your existing stack or suggest the best fit for the project.
Got a website, system, app, or integration to get off the ground?
Tell me what you need. I'll reply within 24h.
Prefer another channel?