Javier
Costa Rosa

Engineering Leader turning technical complexity into product outcomes

I turn ambiguous product problems into reliable systems — aligning architecture, delivery, and AI with real operational needs.

Get in touch View my work
📍 Greater Valencia, Spain · Architecture · Backend Systems · AI in Production
About

I turn product complexity
into systems that hold up.

I work where product, engineering, and operational reality meet: ambiguous requirements, technical trade-offs, delivery pressure, and systems that need to survive beyond the first release.

Over the last 7+ years, I've grown from full stack engineering into technical leadership across architecture, delivery, mentoring, and stakeholder alignment — helping teams ship software that is useful, maintainable, and aligned with the business.

Right now I'm particularly focused on making AI actually useful in production: LLM pipelines, RAG systems, and AI-enabled workflows built around real operational constraints.

Beyond the codebase, I care about the organisational side of engineering: how teams make decisions, how technical direction aligns with business goals, and how to build the kind of culture where good engineering compounds over time.

⚡
Turning ambiguity into technical direction
I help turn unclear product needs into systems that are scoped, designed, and ready to ship.
🏗️
Designing systems that survive growth
I care about reliability, maintainability, and operational clarity beyond the first release.
🤖
Applying AI where it actually helps
I focus on AI where it improves workflows, reduces friction, or unlocks useful product capability.
📈
Leading with leverage in lean teams
I'm most effective in lean teams where technical decisions shape product outcomes directly.
How I work
🧭
On technical direction
Good architecture isn't just about the system. It's about giving the team a clear mental model they can build on without asking permission at every step.
🤖
On AI in products
I'm skeptical of AI features that exist to check a box. I focus on where it removes real friction or unlocks something that wasn't possible before.
⚡
On lean teams
Constraints force clarity. Some of my best technical decisions came from having to choose, not from having unlimited options.
🚢
On delivery
Shipping is the feedback loop. I'd rather iterate on something real than perfect something hypothetical.
Experience
Blue Trail Software

Tech Lead – Product Architecture, Reliability & AI Systems

Aug 2025 – Present
  • Leading the technical evolution of a high-usage crawling product, shaping architecture and reliability for a system used daily by thousands of customers.
  • Drove architectural and reliability improvements across a product used daily by thousands of customers — reducing operational friction and enabling the team to ship new capabilities without compromising stability.
  • Introduced AI-assisted engineering workflows to reduce repetitive work and increase delivery leverage in a lean team.
ArchitectureAI/LLMsObservability

Tech Lead – Product Engineering under Platform Constraints

Nov 2024 – Aug 2025
  • Led a team of 5 evolving a browser-based product under strict platform and product constraints.
  • Defined a maintainable architecture that balanced short-term delivery pressure with long-term product evolution.
  • Explored and validated AI-driven features that could create real user value within tight technical constraints.
Team LeadBrowser ExtensionAI Features

Tech Lead & Solutions Architect

Apr 2023 – Oct 2024
  • Full technical ownership end-to-end: architecture, AWS infra, team leadership, and client interaction.
  • Replaced a fragile, manual workflow with a purpose-built platform — eliminating a category of operational errors and giving the client a system they could actually scale.
  • Led a separate marketplace initiative, guiding junior developers through architecture decisions and end-to-end delivery.
AWSHealthcareSolutions Architecture

Senior Full Stack Engineer

Mar 2021 – Apr 2023
  • Key contributor in a ~10-person team evolving a monolith into a microservices architecture (~10 services).
  • Introduced TypeScript and NestJS to standardize backend development and make a growing codebase easier to maintain across services.
  • Mentored junior developers and launched weekly Tech Talks to strengthen engineering culture.
Node.jsTypeScriptNestJSMicroservices
ITI – Instituto Tecnológico de Informática

Full Stack Engineer – R&D

Feb 2018 – Mar 2021
  • Started as intern, grew into Full Stack Engineer in R&D on national and European innovation projects.
  • Worked across AI, IoT, and blockchain domains using Angular, Vue, NestJS, Node.js, and Python.
  • Applied clean architecture and containerized applications with Docker.
R&DAIIoTBlockchainPython
Selected work

Healthcare workflow automation

Tech Lead & Solutions Architect · Blue Trail Software

Replaced spreadsheet-heavy operations with a dedicated platform, improving reliability and making the workflow easier to scale and maintain. Took full ownership from architecture through delivery, working directly with the client.

HealthcareAWSSystem Design

Browser extension under platform constraints

Tech Lead · Blue Trail Software

Led architecture and delivery for a consent management browser extension operating under strict platform rules. The challenge was balancing maintainability, evolving product needs, and a constrained extension environment — while keeping a team of 5 moving.

Browser ExtensionTeam LeadArchitecture

AI inside production workflows

Tech Lead · Blue Trail Software

Worked on LLM-based and retrieval-enabled features designed around real user flows and operational constraints rather than isolated demos. Also introduced AI-assisted engineering workflows to accelerate delivery within a lean team.

LLM PipelinesRAGAI Product Features
Core strengths
Leadership & Strategy
Technical strategy, engineering culture, stakeholder alignment, team development, delivery ownership
Technical StrategyEngineering CultureStakeholder AlignmentTeam DevelopmentTechnical RoadmapDelivery OwnershipOrg-level Decision Making
Technical Leadership
Architecture, delivery ownership, technical direction, mentoring, stakeholder alignment
Tech LeadArchitectureDelivery OwnershipTechnical DirectionMentoringStakeholder AlignmentTechnical Roadmap
Backend and Distributed Systems
Node.js, TypeScript, Python, NestJS, API design, distributed systems, reliability
Node.jsTypeScriptPythonNestJSAPI DesignMicroservicesDistributed SystemsReliability
Applied AI
LLM pipelines, RAG systems, prompt workflows, OpenAI API integration, AI-enabled product features
LLM PipelinesRAG SystemsPrompt EngineeringOpenAI APILangChainAI Product Features
Infrastructure and Reliability
AWS, Docker, CI/CD, observability, fault tolerance
AWSDockerCI/CDObservabilityFault ToleranceOpenShiftAKS
Data and Messaging
PostgreSQL, MongoDB, Redis, RabbitMQ, Neo4j
PostgreSQLMongoDBRedisRabbitMQNeo4jMySQL
Education
2018 – 2020
Universitat Politècnica de València (UPV)
Master's Degree · Software Engineering, Formal Methods and Information Systems
Thesis: Design and development of a Java program slicer based on the System Dependence Graph
2014 – 2018
Universitat Politècnica de València (UPV)
Bachelor's Degree · Informatics Engineering
Contact

Need technical leadership beyond implementation?

Whether you're shaping a new product, scaling an existing system, or figuring out where AI genuinely fits — I'm open to the right conversations.

LinkedIn hello@javiercostarosa.com