Freelancer profile translated to English.
Back to original languageAbout Javier
Do you need to integrate Artificial Intelligence into your business, create a voice agent, or scale a complex SaaS product?
I'm Javier, a Senior Full Stack Engineer specializing in generative AI ecosystems and high-performance web architectures. I build robust digital products that solve real business problems, such as reducing operational costs or improving user experience with ultra-low latency (<50ms).
How can I help you?
• Real-Time AI and Voice Agents:Design and development of conversational assistants (Voice and Text) integrating Gemini Live API, OpenAI, and WebSockets for fluid, delay-free interactions.
• Multi-tenant SaaS Development:Creation of complete and secure platforms from scratch using the modern ecosystem: Next.js (15/16), React 19, and Node.js (Fastify, Express).
• RAG (Retrieval-Augmented Generation) Pipelines:Connecting your enterprise database with AI models to answer using your business's exact context (Vertex AI, PostgreSQL FTS, Pinecone).
• E-commerce & Automation:Headless solutions, complex task automation (GCP orchestration), and AI-driven asset generation (demonstrated 90% cost reduction).
My Core Stack:TypeScript, Python, Next.js, Node.js, Bun, Web Audio API, Docker, GCP, SQL/NoSQL databases, and event-driven architectures.
I work with a product mindset, taking full technical ownership so you can focus on your business.
I am available to start immediately.Write to me, tell me about your project, and let's evaluate how I can bring you value from day one.
Spanish
Native or bilingual
English
Conversational
Can work on-site
Alicante (up to 50km)
Experience
- boton.ONESenior Full Stack AI EngineerSOFTWARE PUBLISHINGSeptember 2024 - Today (1 year and 9 months)Alicante, SpainIndependent consultant and developer under the commercial brand "boton.ONE", specializing in the design of Full Stack Generative Artificial Intelligence solutions, real-time voice applications, and scalable SaaS architectures.During this period, I have led the architecture and development of multiple products (own and for clients), taking on the complete software lifecycle:🔹 Real-Time AI Architecture: Design of bidirectional audio gateways (Node.js/WebSockets) integrating the Gemini Live API. Implementation of on-the-fly audio transcoders (G.711 to PCM16), achieving fluid voice interactions with ultra-low latency (<50ms) for conversational assistants.🔹 Multi-tenant SaaS Platform Development: Engineering of monorepos (Next.js 15/16, React 19, Fastify) orchestrated via GCP Tasks. Development of secure systems with immutable billing, OAuth session persistence, and execution of complex tools (Tool-Calling for Google Calendar).🔹 Enterprise RAG Systems: Building high-performance RAG pipelines by synchronizing full-text search (FTS) in PostgreSQL with Vertex AI and OpenAI embeddings, injecting business context into live audio streams at sub-millisecond speeds.🔹 E-commerce & 3D Asset Generation: Creation of Headless solutions (Next.js + Shopify) integrated with custom Python LLM pipelines to generate 3D meshes from 2D images, reducing asset creation costs by 90%.🔹 Optimization and Security (High Concurrency): Development of viral web applications supporting high traffic loads, hardening security with strict CSP directives and bot mitigation through rate-limiting in Express.Technology Stack: Next.js 15/16, React 19, Node.js (NestJS, Express, Fastify), Python, TypeScript, Gemini Live API, OpenAI, GCP, PostgreSQL, Docker, WebSockets, Web Audio API.
- Proyectos E-commerceLead Full Stack DeveloperE-COMMERCEJanuary 2024 - July 2024 (6 months)Alicante, SpainTechnical leadership and Full Stack development for various independent projects, focusing on Headless e-commerce, automated marketing tools, and high-traffic web applications.During this period, I was responsible for:🔹 Headless E-commerce & 3D AI: Development of an e-commerce solution combining Next.js and the Shopify API. I integrated a custom Python LLM pipeline capable of generating 3D assets and meshes from simple 2D images, achieving a 90% reduction in store asset creation costs.🔹 Marketing SaaS and Video Automation: Engineering of a monorepo (Next.js 16, Fastify, Remotion) for massive, programmatic video ad generation. Orchestration of the system via GCP Tasks and pioneering implementation of "Chrome Built-in AI" for zero-latency on-device translations.Key Technologies: Next.js, Shopify (Headless), Python (LLMs), Node.js (Express, Fastify), Remotion, Google Cloud Platform (GCP).
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