Xavier Mas Leszkiewicz

BlueBerryBytes

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)

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

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)

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

Retention-Marketing Automation Platform (React, Node.js, ClickHouse, AWS): • 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

• 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

• 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

• 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).