JAVIER UANINI
Software Engineer · Founder & CEO of Siblings Software
FOUNDER & CEO
Javier Uanini is the founder and CEO of Siblings Software, a software development company headquartered in Córdoba, Argentina — one of the fastest-growing tech hubs in Latin America. He leads a team of roughly 30 engineers building products for clients in fintech, healthcare, construction, and logistics.
His relationship with technology started early. In 1999, using a Windows 98 desktop, an Arcor dial-up connection, and a copy of Microsoft FrontPage, he published his first website. He was twelve. By the time he reached high school, he was already spending afternoons writing small programs in Visual Basic and tinkering with HTML tables and inline styles — years before CSS was something you could rely on across browsers.
He went on to study Software Engineering at Universidad Tecnológica Nacional (UTN), Facultad Regional Córdoba, where he met his future co-founders Maximiliano Tomassi and José Obregón. College shaped more than his technical skills — it gave him a network of people who later became the backbone of the company.
After graduating, Javier moved to New York City to work in the payment processing industry. It was there that he encountered the complexity of financial systems at scale: PCI compliance, real-time transaction routing, multi-currency settlement engines, and the relentless pressure of zero-downtime deployments. Those years left a lasting mark on how he thinks about software architecture and operational reliability.
He returned to Córdoba with a plan. In 2018, he and his sister Constanza Uanini founded Siblings Software. The name was literal — a company built by siblings. Maximiliano and José joined immediately, and the four of them took on the first projects out of a small office near downtown Córdoba. There was no external funding, no accelerator, no pitch deck. Just contracts, delivered code, and word of mouth.
From freelancers to a 30-person engineering team
The early days of Siblings Software looked nothing like a typical tech startup. Javier and Constanza started as freelancers, picking up development contracts wherever they could. Their first clients were small businesses in Argentina that needed custom web apps — inventory systems, internal dashboards, payment integrations. Nothing glamorous, but each project built trust and sharpened their delivery process.
By 2020, the team had grown to ten people, all working remotely across Córdoba. The pandemic, paradoxically, accelerated growth: international companies that had been hesitant about remote teams suddenly had no choice. Siblings Software's timezone overlap with the US East Coast (UTC−3) and their fluency in English made them a natural fit for American startups looking for engineering capacity without the overhead of a San Francisco salary.
In March 2021, the company incorporated as an LLC in Florida, establishing a legal presence in the United States. This wasn't about relocation — the engineering team remained in Córdoba — but it simplified contracts, invoicing, and compliance for US-based clients. Today, Siblings operates as a dual-presence company: American entity, Argentine talent.
Javier's leadership style is hands-on. He still reviews architecture decisions, participates in sprint planning, and writes code when a deadline needs an extra pair of hands. He's not the kind of CEO who retreats into spreadsheets. Engineers at Siblings regularly describe the culture as "flat" — you can ping Javier directly on Slack, and he'll answer the same afternoon.
Want to learn more about the team? Meet our full engineering leadership, or explore the projects we've delivered across industries.
Industry expertise and technical depth
Javier's technical background spans the full stack, but his deepest experience is in domains where software touches money, health, or operational logistics — systems where bugs aren't just inconvenient, they're costly.
Fintech & payment processing
Before founding Siblings, Javier spent years in the payment processing industry in New York. That experience now shapes how the company approaches fintech projects: PCI-DSS compliance by default, idempotent transaction APIs, real-time reconciliation pipelines, and thorough audit logging. The team has built payment gateways, digital wallet backends, and KYC verification flows for clients in both the US and Latin America. You can see one example in the SUR Technology Holdings case study.
Healthcare software
Healthcare has been a recurring vertical. The team has built clinical data platforms, appointment scheduling systems, and remote patient monitoring applications. These projects demand careful attention to data privacy, role-based access control, and reliable uptime — you can't have a patient-facing app go down during a consultation.
Construction & logistics
In the construction sector, Javier has led projects involving project management dashboards, real-time field reporting apps, and inventory tracking systems that bridge the gap between office and jobsite. More recently, the team delivered a distributor web portal for Bari that streamlined order processing and reduced manual data entry by over 60%.
Preferred stack
For modern web products, the team's go-to stack is React + Next.js + Node.js deployed to Vercel. This combination gives them fast iteration cycles, strong SEO out of the box (thanks to SSR/ISR), and a deployment workflow that eliminates most DevOps overhead. For mobile, the team works with React Native, Swift, and Kotlin depending on the project's constraints. Backend services frequently run on Node.js with TypeScript, Express or NestJS, PostgreSQL, and Redis.
Case snapshot: rebuilding a payment gateway under pressure
In late 2022, a US-based fintech client came to Siblings Software with an urgent problem. Their existing payment gateway — originally built by a contractor who had since left the project — was failing intermittently during peak transaction hours. Chargebacks were climbing, and their payment processor threatened to suspend the account.
Javier led the assessment personally. Within the first week, the team identified three critical issues: a race condition in the transaction settlement queue, missing idempotency keys on retry logic, and a database connection pool that exhausted under concurrent load. None of these were visible in the codebase at a surface level — they only appeared under production traffic patterns.
The team rebuilt the gateway's core pipeline in Node.js with TypeScript, introduced proper queue-based processing with BullMQ and Redis, and added comprehensive monitoring through Datadog. The entire migration was completed in six weeks without a single minute of downtime for the client's merchants.
Results: transaction failure rate dropped from 3.2% to 0.1%, chargeback disputes decreased by 74%, and the client passed their next PCI audit with zero findings. The relationship continues — Siblings now maintains and extends the platform with a dedicated three-person squad.
More client stories: browse our full case study library.
Why Córdoba, Argentina
Javier chose to build Siblings Software in Córdoba for reasons that go beyond personal attachment. The city has over 330 technology startups and continues to climb in global ecosystem rankings — jumping from 318th to 226th worldwide in just four years, according to the Startup Genome report.
The talent pipeline is deep. Córdoba's 14 universities graduate thousands of engineering students every year, and the province's literacy rate sits at 98.5%. The UTN campus alone produces a steady stream of Information Systems engineers who are immediately competitive in backend, frontend, and mobile development roles.
Córdoba also sits in the UTC−3 timezone, which means full workday overlap with US Eastern Time clients and significant overlap with European teams. For Javier, this geographic advantage was deliberate: it allows Siblings to operate as a nearshore partner without the friction of asynchronous communication across distant time zones.
The cost of living in Córdoba is substantially lower than Buenos Aires or major US cities, which translates directly into competitive rates for clients without sacrificing engineer compensation. It's one of the reasons Siblings has been able to retain talent at a rate well above the Argentine industry average.
Resources & communities Javier follows
A selection of external resources that inform how Javier and the team approach software development:
- Martin Fowler — Software Architecture — patterns for distributed systems and microservices
- DORA Metrics — measuring engineering team performance and delivery velocity
- Next.js Documentation — the framework at the center of Siblings' preferred web stack
- Node.js API Docs — reference for backend development
- DEV Community — where Javier and teammates share technical posts
- Siblings Software — Wikipedia — company background and history
Interested in working with Javier's team? Get in touch, or explore open positions if you'd rather join than hire.