Cristian (Serje) R.
Team Lead Mobile Native Apps
Experience
Apr 2019 - Present
6 years 8 monthsMunich, Germany
Team Lead Mobile Native Apps
Check24 GmbH
- Built and managed a high-performing native app team (Android & iOS) from scratch.
- Modernized the finance application with new features, leveraging Kotlin, Java, and Spring Boot microservices.
- Introduced and scaled backend services enabling secure, high-traffic financial transactions for millions of users.
- Improved development efficiency with custom tools for crash reporting, CI/CD pipelines, and release management.
- Led recruitment, coaching, and mentoring of developers, fostering professional growth and cross-functional collaboration.
Aug 2016 - May 2019
2 years 10 monthsMunich, Germany
Senior Mobile Engineer
Check24 GmbH
- Designed and developed a new Android finance application from scratch.
- Architected and implemented backend microservices (Java, Spring, REST APIs) powering both iOS & Android apps.
- Built reusable frameworks to accelerate app development across Check24.
- Scaled systems to support 5M+ active users securely and reliably.
Nov 2011 - Aug 2016
4 years 10 monthsMunich, Germany
Senior Software Engineer
Insparx GmbH
- Delivered Android features and backend solutions using Java (EJB, JMS) and Python GAE.
- Designed backend messaging and notification systems with NoSQL and search integrations.
- Integrated payment providers and external APIs into backend clusters running on JBoss.
Mar 2010 - Oct 2011
1 year 8 monthsLisbon, Portugal
Java and Software Senior Developer
TMN - Portugal Telecom Sistemas de Informação
- Development of business applications in one of the biggest and most important Portuguese companies in Technology, Communication and Information Systems, working on different teams with innovative and challenging projects.
- Designing and implementing the architecture of several projects such as a sending system for SMS and MMS (EasyMessaging) TMN, whose business layer provides services via web, used mainly by the public portal for sending SMS and MMS to mobile networks (e.g., TMN, Vodafone) but also available for external systems via Web Services (SOAP protocol) and Common Gateway Interface (CGI), and developing, leading, and designing different projects for external and internal company use using different technologies and frameworks.
Oct 2008 - Oct 2009
1 year 1 monthMedellín, Colombia
IT Coordinator/Senior Developer
DownUnderGroup SA
- Headed the information system area, coordinating IT affairs in the hotel chain, developing applications in C++ and Java, updating and developing websites, client database, and bookkeeping systems.
- Checked the work of local team and other teams in the branch.
- Coordinated a four-person team to maintain the different systems.
- Performed data integrity checking.
- Modified site using CMS.
Jun 2007 - Jul 2008
1 year 2 monthsMaringá, Brazil
Software Architect and Developer, Team Leader
SG Sistemas
- Developing and leading software projects for the automation of companies, working with PDAs, web development, and software development.
- Designing and developing mobile applications to offer better service to customers, with wireless update and compatibility with Brazilian mobile networks (Android, iPhone, Symbian, Palm, Blackberry).
- Implementing web applications to check partners information through the database of Cidade Canção, a Brazilian market chain (SQL Server, MySQL, Tomcat, ActionScript, XML, Struts).
- Completed development of an in-house remote administration app to manage employees remotely (Java, C++ Builder, HTML, sockets).
Oct 2006 - May 2007
8 monthsBarranquilla, Colombia
Programmer, Consultant
Sigma
- Developed applications specified by the customer.
- Worked on different projects and programming languages, Java, C++.
- Provided customer technical support.
- Developed web applications in JSP and reports using iReport.
Summary
Engineering Team Lead with 15+ years of experience building mobile applications and scalable backend systems used by millions of users across Europe and Latin America. Proven expertise in Native Android development, Java, Backend, Microservices, Cloud and Skilled in leading and mentoring cross-functional teams, delivering high-performance solutions, and driving Cristian Serje Reyes innovation in fintech, telecom, and large-scale consumer platforms.
Languages
Spanish
NativeGerman
AdvancedEnglish
AdvancedPortuguese
AdvancedItalian
IntermediateEducation
Jan 2003 - Mar 2007
Universidad del Norte
Computer Science Engineer · Computing · Barranquilla, Colombia
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