Inconsistent patterns across the product
Similar problems get solved in different ways across the UI, API, state, data models, and integrations — increasing bugs, friction, and review time.
Senior full-stack product engineering for B2B SaaS teams with complex products
I help B2B SaaS teams move from product complexity to shipped software — improving frontend architecture, backend APIs, integrations, workflows, and the technical decisions that slow delivery down, while identifying where AI can remove real friction.
- Dashboards, workflows, APIs, integrations, permissions, product logic, and AI-powered features
- Vue, React, TypeScript, Node.js, databases, LLM APIs, and modern product stacks
- Direct senior execution across the stack, no layers, no handoff overhead
18+ years building production software across SaaS, healthcare, industrial systems, complex workflows, and long-lived products
Where B2B SaaS teams usually get stuck
When delivery slows down, the problem is rarely just "more frontend work" or "more backend work." It is usually product complexity spreading across the stack: unclear data flows, fragile architecture, inconsistent patterns, integrations, permissions, and workflows that keep growing sprint after sprint.
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Architecture starts working against delivery
Coupling grows between frontend, backend, product logic, and data flows until simple changes require too much coordination and too much risk.
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Product logic keeps compounding
Forms, permissions, state, workflows, validations, and edge cases pile up until simple changes stop feeling simple.
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Data-heavy workflows become slow and fragile
Dashboards, tables, filters, reports, imports, exports, and API calls start hurting usability and engineering speed at the same time.
I help teams standardize patterns, simplify product architecture, connect frontend and backend decisions, and improve the parts of the system where complexity slows delivery the most.
What better product engineering should unlock
- Faster feature delivery with less regression risk
- Clearer patterns across frontend, backend, and product logic
- Less time lost to fragile workflows and unclear ownership
- Better maintainability as the team, codebase, and customer needs grow
- More confidence shipping on top of an existing product
- Fewer handoffs between product thinking, frontend execution, backend changes, and delivery
- AI features that ship into production — with sensible UX, predictable behavior, and controlled costs
AI integrated into your product and processes
Most teams don't need an "AI strategy." They need someone who can take a real process — support, onboarding, reporting, data entry, document handling, coaching, QA — and ship a working AI feature inside the product they already have.
That's full-stack work: data flows, APIs, prompts, evaluation, UX, fallbacks, and cost control. The same engineering discipline I bring to the rest of your product.
Where AI usually pays off in B2B SaaS
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In-product assistants and copilots
Contextual help, guided setup, or domain-specific coaching built on your own product data. -
Document and data workflows
Extraction, classification, and summarization for imports, reports, tickets, contracts, or compliance documents. -
Internal process automation
Turning repetitive operational work — triage, tagging, drafting, review — into AI-assisted workflows your team controls. -
Smarter search and insight
Semantic search, Q&A over internal knowledge, and dashboards that explain instead of just display.
Selected work
A few examples of the kind of products, systems, and teams I've supported across the stack.
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Sports event platform with an in-product AI coach
A product-led sports platform for tournament organization, live results, sponsor visibility, and community engagement. Includes Match Flow, a live match tracker with an AI coach that reads the momentum of a tennis or padel match and gives players real-time insight while they play — LLM integration, live data flows, and sport-specific prompt design built into a production feature.
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Cross-platform rewrite for the world's most translated digital platforms
Complete rewrite of a 14-year-old cross-platform study app — unifying separate iOS, Android, and desktop codebases into a single modern frontend serving 1,000+ languages and tens of millions of users. Contributed atomic UI components, end-to-end user workflows, and a deep research interface, in close collaboration from design spec to production.
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Industrial engineering platforms for compliance-sensitive workflows
Browser-based tools used in German engineering environments with structured technical data, validation logic, backend workflows, production data, release automation, and high-trust operational requirements.
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Medical visualization platform
A Three.js + Vue application for advanced dental and craniofacial scan analysis, high-resolution imaging, complex planning workflows, and production-grade user interaction around heavy visual data.
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Public-sector health systems
Long-lived public-sector health systems with real operational pressure: patient records, databases, reporting tools, internal workflows, user training, and continuity requirements.
Trusted by teams that needed senior execution
How I usually work with teams
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01 Product and technical context
We align on the product, the users, the business constraints, the current stack, delivery friction, and the kind of support that would actually help.
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02 Stack and workflow audit
I identify the highest-leverage issues across the frontend, backend, data flows, integrations, architecture, and product workflows — including where AI could remove real friction, and where it would just add complexity.
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03 Senior execution
I work directly inside the product to ship improvements across the stack with clear priorities, pragmatic tradeoffs, and practical checkpoints.
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04 Documentation and enablement
Important decisions, patterns, and tradeoffs get documented so the product becomes easier to maintain after I step out.
Direct senior collaboration across the stack. No junior rotation, no dependency trap, no unnecessary process overhead.
Who I work best with
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Great fit if:
- You already have a live B2B product, MVP, or serious prototype
- Your product is getting harder to ship, maintain, or extend
- Your team needs help across frontend, backend, APIs, integrations, workflows, or product logic
- You want senior-level support without committing to a full-time hire yet
- You need someone who can work inside complexity without creating more of it
- You want to integrate AI into your product or internal processes, and you need it built properly — not a throwaway prototype
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Probably not the right fit:
- You only need a simple marketing site or brochure website
- You want the cheapest delivery option
- You need a large agency model with multiple layers
- You want to outsource product thinking completely
- You need someone to follow tickets blindly without questioning product or technical tradeoffs
About Saulo
I’m Saulo Vargas, a senior full-stack engineer with 18+ years building production systems across SaaS, healthcare, industrial platforms, public-sector software, sports tech, and long-lived product codebases.
Frontend has been one of my strongest edges for years, but most of my work has never been frontend-only. I’ve built interfaces, backend APIs, databases, integrations, internal tools, operational workflows, and production systems used by real teams in real environments. More recently, that includes integrating LLMs into production features — like the AI match coach I built for EntrenoLibre’s Match Flow.
RusticIT is my independent practice for working directly with teams that need senior product engineering support across the stack.
@saulovargas
Available
Saulo Vargas
Senior Full-Stack Engineer
Need help turning product complexity into shipped software?
If product complexity is slowing delivery — or you know AI could improve your product or processes but nothing has shipped yet — I can help you find the real bottlenecks and work on the fixes that improve velocity, quality, and maintainability.
I'll reply personally and let you know quickly whether I'm the right fit.
Prefer reading first? Read Beyond CodeTell me what your team is dealing with
Share a bit of context about your product, your stack, the delivery bottlenecks you're dealing with, or the kind of support you need. I'll review it personally and get back to you.