# Xavier Mas Leszkiewicz

Distributed systems & ML in production — Telefónica, Elliptic, eDreams and General Motors projects

## About
Engineering leader with 10+ years building distributed systems, cloud and AI products at scale — terabyte-scale event pipelines at Telefónica, blockchain forensics at Elliptic, ML model serving at eDreams' search traffic, and serverless architecture for General Motors. Founder & CTO at BlueBerryBytes, serving as fractional CTO for funded startups: hands-on architecture, team leadership, and a product of my own shipped end-to-end (Plan AI).

## Professional Experience

### BlueBerryBytes - Founder & CTO
Leading engineering across 4 funded startups in parallel (~8-10 engineers); built and hired BlueBerryBytes' own 4-engineer team.
• Dawlati: lead technical authority — AWS architecture, engineering operations and technical strategy for their digital platforms.
• Qantara Sports (Impakt): technical strategy, cloud database architecture and AI integration for a sports talent acquisition platform.
• House Group / House of AI: AdTech data pipeline and production AI prototypes for corporate clients.
• Dress Up: fractional CTO — technical architecture and scaling of a consumer AI platform.
• Built and open-sourced Plan AI: a bot-free meeting recorder (Electron, BullMQ, Qdrant) that turns meetings into Jira tickets and architecture diagrams.


### Lumenalta (formerly Clevertech) - Senior Software Engineer
General Motors — Alert & Notification System (TypeScript, AWS):
• Designed and built a serverless system delivering alerts and incident notifications into GM's platform (API Gateway, Lambda, DynamoDB).
Swap Health (Ionic, React, Firebase, Google Cloud):
• Developed a cross-platform mobile app (iOS/Android) with offline sync, push notifications and real-time analytics.
• Integrated Firebase Authentication and Firestore, improving data consistency and security.
• Built a custom analytics dashboard allowing stakeholders to track user engagement.


### Elliptic - Senior Full-Stack Software Engineer
Cross-Chain Forensics Platform (React, D3.js, Java, Scala, AWS):
• Led feature delivery as second-in-command of a ~15-person product team on Elliptic's blockchain investigation product.
• Built graph-based visualization of cross-chain crypto fund flows used by institutional compliance analysts (React, D3.js).
• Collaborated on Java/Scala backend services consuming the data team's blockchain intelligence.


### Full On Net (Telefonica) - Senior Software Engineer
Telefonica IPTV Data Infrastructure (Python, Kafka, Kafka Streams, MongoDB, Celery):
• Merged Spain and LATAM IPTV event infrastructure — two continents unified into one terabyte-scale pipeline serving millions of households.
• Built the data-processing modules (transformation, aggregation, async processing) consuming Kafka streams into MongoDB.


### Relevanzz - Co-Founder and CTO
Retention-Marketing Automation Platform (React, Node.js, ClickHouse, Google Cloud):
• Built a platform that ingested e-commerce purchase data via API and Shopify into ClickHouse for behavioral segmentation.
• Automated Facebook/Instagram campaigns triggered daily by purchase patterns (e.g. "bought brand X, inactive 30 days" → targeted creative).
• Owned the full stack as technical co-founder: ingestion, segmentation engine and campaign activation.


### eDreams ODIGEO - Software Engineer - Machine Learning POD
• Productionized the data science team's ML models at eDreams' search scale: Java serving APIs handling tens of thousands of requests per minute.
• Deployed models as PMML (XML) with strict timeout budgets and load balancing to protect search latency.
• Built and operated the supporting pipelines and observability (Kafka, Kubernetes, Docker, Elasticsearch/Kibana).


### eDreams ODIGEO - Java Developer - BI Revamp
• Developed distributed data-processing services for eDreams' BI platform (Java, SQL, MongoDB).
• Automated CI/CD pipelines with Maven and Kubernetes, substantially reducing deployment time.
• Implemented data aggregation and transformation strategies that cut reporting query times.


### SIA Group. Sistemas Informáticos Abiertos - Java Developer and IT Security
• Worked in a high-security government environment, managing 250,000+ identities with Single Sign-On (SSO) and identity protection.
• Led the migration of legacy applications to a modern identity management system.
• Developed Java-based security applications integrating Active Directory, Oracle Identity Manager and Siteminder (SSO).


## Education

### UPC School. School of Professionals & Executive Development - Postgraduate in Quantum Engineering
2023


### UPC School. School of Professionals & Executive Development - Big Data Management & Analytics
2016


### UPC. Universitat Politècnica de Catalunya - Bachelor degree in Audiovisual Systems
2015


### Technische Universität Berlin - Bachelor Thesis
2015


## Skills
- Technology Leadership
- Software Architecture & Distributed Systems
- AWS & Cloud Infrastructure
- AI / ML & LLM Systems
- Data Engineering & Kafka
- Team Building & Mentorship

## Online Presence
- [linkedin](https://www.linkedin.com/in/xavier-mas-leszkiewicz/)
- [github](https://github.com/masosky)
- [twitter](https://twitter.com/xmasle)
- [youtube](https://www.youtube.com/@xaviermasle)
- [instagram](https://www.instagram.com/masleszkiewicz/)
- [Portfolio](https://blueberrybytes.com)