Wojtek Wajerowicz, Developer in Geneva, Switzerland
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Wojtek Wajerowicz

Verified Expert  in Engineering

Back-end Developer

Geneva, Switzerland
Toptal Member Since
September 6, 2022

Wojtek is a back-end software engineer with a master's degree in telecommunications and computer science. He specializes in Scala development and has significant expertise in functional programming and building scalable web services. He has also worked with big data technologies like Spark and event sourcing/streaming architecture like Kafka. Wojtek has contributed to the back-end development of meaningful projects, including a diagnostic implementation simulator for SARS-CoV-2.


Scala, Http4s, Apache Kafka, Circe, SBT, Amazon Web Services (AWS)...
Scala, Akka, Akka HTTP, Akka Persistence, Circe, Apache Cassandra...
Equal Experts (Contract)
Scala, Java, MongoDB, Java 11, Back-end, REST




Preferred Environment

MacOS, IntelliJ IDEA, SBT

The most amazing...

...thing I've developed was Blue Brain Nexus, a knowledge graph supporting Blue Brain Project's brain simulation efforts.

Work Experience

Senior Software Engineer

2021 - 2022
  • Contributed to developing the architecture and implementing the scalable microservice back end.
  • Gathered requirements and developed new features for the REST API backing a wholesale marketplace website.
  • Delivered new features for the website as part of a cross-functional team.
Technologies: Scala, Http4s, Apache Kafka, Circe, SBT, Amazon Web Services (AWS), Amazon DynamoDB, PostgreSQL, Functional Programming, Back-end, REST, APIs, Cloud, Microservices, Architecture, Scalable Application, Scalable Web Services, Scalable Architecture, Distributed Systems

Back-end Scala Developer

2017 - 2021
  • Contributed to the architecture design and services implementation, enabling Blue Brain Project's data-driven science using Semantic Web technologies such as RDF, JSON-LD, and SHACL.
  • Developed Scala HTTP microservices for Blue Brain Nexus using the Akka framework, functional programming with Cats and Monix, and Apache Cassandra and Elasticsearch.
  • Deployed services on OpenShift Container Platform and Kubernetes with monitoring and alerting.
Technologies: Scala, Akka, Akka HTTP, Akka Persistence, Circe, Apache Cassandra, Functional Programming, Kubernetes, Red Hat OpenShift, OpenShift, Open Source, Git, GitHub, Elasticsearch, Blazegraph, RDF, JSON-LD, REST, Back-end, APIs, Microservices, Architecture, Scalable Architecture, Scalable Application, Scalable Web Services

Software Developer

2016 - 2017
Equal Experts (Contract)
  • Developed Scala REST API microservices using the Play Framework, Akka HTTP, and MongoDB.
  • Contributed to the application's design and architecture with a high emphasis on security.
  • Implemented the OAuth2/OpenID Connect specification for login.
  • Ported and maintained legacy Java Spring applications.
Technologies: Scala, Java, MongoDB, Java 11, Back-end, REST

Software Developer

2015 - 2016
Job Board for Contract Work
  • Led the transition from a custom-made data pipeline to Apache Spark, resulting in a ten-fold improvement in performance.
  • Developed a data processing pipeline using Apache Spark with GraphX on Amazon EMR.
  • Introduced Scala and functional programming to the tech stack.
  • Implemented the search feature in Java REST API using Elasticsearch.
Technologies: Scala, Elasticsearch, Spark, Amazon Elastic MapReduce (EMR), Back-end, APIs, REST, Cloud, ETL, Big Data

Software Engineer

2015 - 2015
MetaBroadcast (Contract)
  • Developed a highly available REST API with a 99.99% uptime rate for a TV content metadata using Java 8, Cassandra, MongoDB, and Kafka.
  • Implemented data ingestion from multiple sources into the main data store.
  • Configured the infrastructure running on AWS using Puppet.
Technologies: Java, Cassandra, Amazon Web Services (AWS), Apache Kafka, Back-end, APIs, REST, Cloud, Microservices, Scalable Web Services, Scalable Architecture

Senior Software Engineer

2011 - 2014
  • Developed big data processing pipelines aggregating data.
  • Build a REST API supporting the client-facing front-end application.
  • Mentored junior team members in Java and current software development practices.
Technologies: Java, Scala, Spark, EMR, Redis, Cassandra, Apache Kafka, Back-end, REST, APIs, Cloud, Microservices, Scalable Web Services, Scalable Application, Scalable Architecture, Big Data, Distributed Systems

Back-end Development of Blue Brain Nexus

A knowledge graph for data-driven science, supporting Blue Brain Project's brain simulation efforts. I was a back-end developer implementing the REST API in Scala based on the Akka Persistence framework. I was also involved in indexing logic, allowing the efficient search and retrieval of stored information.

Back-end Development of a Diagnostic Implementation Simulator

A SARS-CoV-2 diagnostic implementation simulator for the Foundation for Innovative New Diagnostics, a global health nonprofit based in Geneva. I developed the back-end REST API, which created an interface between the simulation code and front end. I introduced modern software development practices to the project, such as source control and CI/CD, and mentored other team members on these practices. The project is open source and can be accessed via github.com/BlueBrain/covid-19-find.
2006 - 2011

Master's Degree in Telecommunications and Computer Science

Łódź University of Technology - Łódź, Poland


Circe, Http4s


Git, SBT, GitHub, IntelliJ IDEA, Amazon Elastic MapReduce (EMR)


Scala, Java, RDF, Python, Java 11


Functional Programming, REST, Microservices, Scalable Application, ETL


Akka, Flask, Spark


Apache Kafka, Amazon Web Services (AWS), MacOS, Kubernetes, Red Hat OpenShift, OpenShift, Blazegraph


PostgreSQL, Elasticsearch, Amazon DynamoDB, JSON-LD, Cassandra, MongoDB, Redis


Back-end, APIs, Cloud, Scalable Architecture, Scalable Web Services, Akka HTTP, Apache Cassandra, Open Source, Architecture, Big Data, Distributed Systems, Akka Persistence, Software Engineering, Electronics, EMR

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