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Xavier Mas Leszkiewicz

Fullstack Developer, Software Architect & Websites

Works remotely from Barcelona

  • 41.3829
  • 2.17743
  • Suggested rate €250 / day
  • Experience 7+ years
  • Response rate 100%
  • Response time A few days
Propose a project The project will begin once you accept Xavier's quote.

This freelancer is available part-time (Evenings & weekends) but hasn't confirmed their availability in over 7 days.

Part-time, Evenings & weekends

Propose a project The project will begin once you accept Xavier's quote.

Location and workplace preferences

Barcelona, España
Remote only
Primarily works remotely


Project length
  • ≤ 1 week
  • ≤ 1 month
  • Between 1-3 months
  • Between 3-6 months
  • ≥ 6 months
Business sector
  • Digital & IT
  • Automobile
  • Biotech
  • Film & AV
  • Civil Engineering
+24 autres
Company size
  • 1 person
  • 2-10 people
  • 11 - 49 people
  • 50 - 249 people
  • 250 - 999 people
+2 autres


Freelancer code of conduct signed
Read the Malt code of conduct

Verified email


  • Spanish

    Native or bilingual

  • Catalan

    Native or bilingual

  • English


  • Portuguese


  • German



Skills (31)

Xavier in a few words

I have Spanish and British citizenship. I am a curious person who looks forward to learning things every day. I am really passionate about technology, teaching, and coaching. I am the author of two Java manuals. I love teaching students and coaching people. I do really like to interact with groups to contribute to my ideas.

Related to technology, my main fields of interest are Java, Big Data, Computer Science, Project Management, and Coaching.

I obtained my postgraduate in Big Data Management and Analytics, Big Data and Data Science from the UPC School of Professional & Executive Development in 2016 and my B.S. in Audiovisual Systems Engineering(Telecommunication degree) from Universitat Politècnica de Catalunya in 2015, after completing my thesis on Object tracking using real-world coordinates at Institut für Nachrichtenübertragung in Technische Universität Berlin.



Solucionar display de un gif para Python  - As a freelancer

Barcelona, España

January 2022 - January 2022

Ayudar a mejorar la visualización de un vídeo animado para un trabajo de investigación.
El trabajo contenía librerías de reconocimiento de voz y el cliente buscaba una forma elegante de poder representar una animación mientras el programa de reconocimiento de voz estaba activo.
Computer vision Python

Full On Net

Software Engineer

Madrid, Community of Madrid, Spain

February 2021 - Today (1 year1 year and 6 months)

Client: Telefonica Role: Software Engineer Project: Merge LATAM and Spain infrastructure for all IPTV events. Technologies: Python, Java, MongoDB, Kafka, Kafka Streams, Celery, Behave


Senior Backend Engineer  - As a freelancer

Arizona, United States

October 2020 - March 2021 (5 months)

Client: CSAA Responsible for designing and developing architectures for the backend. Technologies: AWS (Sam, API Gateway, Lambda, DynamoDB, Parameter Store, Code Pipeline), NodeJs.


Software Engineer  - As a freelancer

New York, United States

July 2020 - October 2020 (3 months)

Client: Waking up with Sam Harris Responsible for designing and developing architectures. Technologies: React, NodeJs, GraphQL, Redis and RRDD


Co-Founder and CTO

Barcelona Area, Spain

June 2019 - July 2020 (1 year1 year and 1 month)

Full SaaS Infrastructure using technologies as: React, Redux, Typescript, NodeJS, SQL, SCSS, Redis, Clickhouse, Bull, GCloud

eDreams ODIGEO

Software Engineer - Machine Learning POD


January 2018 - June 2019 (1 year1 year and 5 months)

Working as a senior software engineer at Machine Learning Team at eDreams Odigeo. My goal is to design and provide a robust back-end infrastructure capable to serve different Machine Learning technologies. I am working really close to Data Science and providing the latest technology to my company. Basically working with Java, Python, Docker, Maven, Kafka, Kuberntes, Kibana, Elastic Search and related technologies.

eDreams ODIGEO

Java Developer - BI Revamp

Barcelona, Spain

January 2017 - January 2018 (1 year1 year)

Working with Java and all related technologies as NOSQL, SQL, Maven, and other technologies. My goal was to treat a big amount of data, treat this data and finally store it. I had complete ownership with this project, since designing until deploying to production.

SIA Group

Java Developer and IT Security


April 2015 - January 2017 (1 year1 year and 9 months)

Working in a government environment involving a wide variety of technologies and different operating systems. Managing more than 250,000 identities and Sign-On protection for these identities. Responsible for migration of many applications and responsible for improving or creating scripts using Oracle Identity Manager Mostly focused on Java applications and similar. Dealing with many technologies as Active Directory, Oracle database, Visual Basic, Oracle Identity Manager, Siteminder (SSO) and frameworks as Spring or Struts.

Private teacher

Private Teacher  - As a freelancer

January 2009 - April 2015 (6 years6 years and 3 months)

Private tuition in mathematics, chemistry, physics and programming

1 project on Malt

(1 rating)



Xavier es una persona muy proactiva y profesional, se preocupa por las necesidades del cliente y está en todo momento pendiente de la calidad y el resultado final del proyecto, además, analiza el conjunto del proyecto y propone ideas ideas que mejoran el resultado. Ha demostrado unos conocimientos muy avanzados en el área de programación en PYTHON. En conclusión, un excelente trabajo. Lo recomiendo¡¡¡¡

Rebeca Giancarlo - Rebeca


Xavier es un profesional muy cualificado y proactivo. Me realizó la creación de un website y contrario a otros freelance con los que he trabajo, Xavier participó activamente en el proyecto y estuvo pendiente de gestionar todas las demandas y necesidades que teníamos para la website. Además de la programación se encargó activamente en el diseño y estética de la web, agradecemos mucho su implicación y el resultado final. Gran profesional y súper recomendable, repetiremos otros proyectos con él seguro!