Alexandros is available for hire

Alexandros Nafas

Verified Expert in Engineering

Software Developer

Athens, Central Athens Regional Unit, Greece

Toptal member since June 8, 2020

Expertise

Back-end Developers Software Development Full-stack Java SQL MySQL Git Microservices Development GitHub Agile Development REST API JUnit Angular

Bio

With over ten years of experience in software engineering working with numerous major clients in various industries, including logistics, tourism, and adtech, Alex has the skills to deliver complete solutions to difficult problems. He enjoys working on various tasks, from the front end to the back end, data engineering, and infrastructure. However, Alex is most intrigued by figuring out what the client really wants and how he can deliver something of value to them.

Portfolio

Bilt Technologies

Java, Google Cloud Platform (GCP), Apache Beam, BigQuery, Data Pipelines...

Mambu

Apache Beam, Stream Processing, Java, Apache Spark, Angular, MySQL...

Syngenta - Digital Product Engineering

Java, Spring Boot, PostgreSQL, Kubernetes, Docker, Amazon Web Services (AWS)...

Experience

Java - 10 years
MySQL - 10 years
Scrum - 6 years
Angular - 5 years
Docker - 4 years
TypeScript - 4 years
Hibernate - 3 years
Apache Kafka - 3 years

Availability

Part-time

Preferred Environment

GitLab, Jira, Git, Slack, WebStorm, IntelliJ IDEA, MacOS, Linux

The most amazing...

...project I've led was building a data pipeline that analyzed traffic quality and blocked fraudulent sources in real-time, resulting in a 30% reduction in fraud.

Work Experience

Java Expert

2024 - PRESENT

Bilt Technologies

Maintained and created new data pipelines in Apache Beam, ingesting gigabytes of transactional data from third-party integrations and pushing events to BigQuery and Pub/Sub.
Migrated data pipelines and built processes to new repositories using Terraform and company best practices.
Introduced Beam YAML API as a way for teams to dynamically spawn their own data pipelines without support from the data team.

Technologies: Java, Google Cloud Platform (GCP), Apache Beam, BigQuery, Data Pipelines, Big Data, Terraform, Google Cloud Build, GitHub Actions, Google Cloud Dataflow

Senior Java Developer

2023 - 2024

Mambu

Worked as part of a team to develop a new financial product for Islamic profit sharing.
Collaborated with the product owners and clients to clarify the requirements and design the system.
Built a streaming pipeline using Apache Beam, which processes events in real-time and updates the current balances of the accounts.
Built an Apache Spark pipeline that processed daily batches of transaction events and generated the profit shares of all accounts.
Migrated the batch pipeline into a Java service that uses SQL queries for profit computations.
Worked on supporting the client and fixing bugs in collaboration with the product owners, after delivering an MVP.

Technologies: Apache Beam, Stream Processing, Java, Apache Spark, Angular, MySQL, Google Cloud Platform (GCP), Kubernetes, Real-time Streaming

Tech Lead

2022 - 2022

Syngenta - Digital Product Engineering

Took over a project of 13 microservices from the previous team and was responsible for discovering the architecture.
Supported a team of front-end engineers, requesting bug fixes and new features being implemented.
Mentored new engineers coming into the project and guided their implementations. Handled the final code approval.
Defined a CI/CD across four environments involving Jenkins, AWS CodeBuild, and GitHub Actions.
Worked on migrating data from the legacy platform into the new one, which involved understanding the business model and making the necessary transformations.
Built a small data pipeline, which pulled data out of the application and ingested it into a data lake used to power reporting tools.

Technologies: Java, Spring Boot, PostgreSQL, Kubernetes, Docker, Amazon Web Services (AWS), Amazon EKS, Jenkins, AWS CodeBuild, Apache Kafka, Kafka Streams, Integration Testing, Relational Databases, Java 11, JUnit, Mockito, Ubuntu, Bash Script, GitOps, DevOps Engineer, REST, Infrastructure as Code (IaC), AWS Lambda, Apache, Azure, Lambda Functions, React, Jest, Amazon Simple Queue Service (SQS), Amazon Simple Notification Service (SNS), Redis

Principal Software Engineer

2021 - 2022

Priceline

Implemented new integrations with Booking.com updated APIs.
Containerized and migrated apps from on-prem servers to GKE.
Replaced calls to the legacy Oracle database with Netflix Hollow in-memory cache solution.
Migrated CI/CD processes from Bamboo to GitHub Actions.

Technologies: Java, Spring, Spring Boot, Kubernetes, Google Cloud Platform (GCP), Google Kubernetes Engine (GKE), Docker, Oracle Database, GitHub, Software Development, Relational Databases, Java 11, JUnit, Mockito, Ubuntu, REST, Oracle

Technical Lead

2018 - 2021

Glispa Global Group

Served as a technical lead on the Glispa Performance Network, one of the top advertising affiliate networks with numerous partner integrations, earning more than a million dollars in revenue per month.
Worked as a front-end developer building external analytics dashboards and maintaining the company's main internal platform in Angular.
Acted as a data engineer, automating event data ingestion from Kafka, using Python and Scala Spark to process events and present results to dashboards built with Angular and Turnilo.
Led a big project of building a data pipeline that analyzed traffic quality and blocked fraudulent sources in real-time. The result was a 30% reduction in fraud as well as freeing up the account managers who had to do this task manually before.
Used Kubernetes and GitLab CI for automating the deployment of all microservices.
Worked as a scrum master and helped clarify processes and ease the transition of the Athens department from being a startup to being part of a large organization with multiple departments and stakeholders around the world.

Technologies: Slack, IntelliJ IDEA, MacOS, Vert.x, Continuous Integration (CI), Architecture, GitLab, Jira, WebStorm, Linux, Spark, MongoDB, Spring, NoSQL, Continuous Deployment, DevOps, TypeScript, JavaScript, Amazon Web Services (AWS), Scrum, Git, MySQL, SQL, Ansible, Kubernetes, Docker, BigQuery, Druid.io, Hadoop, Angular, Apache Kafka, Python, Scala, Java, Node.js, BigTable, Google Bigtable, Google BigQuery, Google Cloud Platform (GCP), Cloud Dataflow, Data Engineering, Back-end, Spring Boot, CI/CD Pipelines, Metabase, ETL, Data Pipelines, NgRx, Continuous Delivery (CD), Monitoring, PHP, SonarQube, Systems Monitoring, Unit Testing, Agile, Confluence, Full-stack, API Connectors, REST APIs, Microservices, APIs, OpenAPI, Data Architecture, Big Data, Data Warehousing, Software Development, Cloud Architecture, React, Integration Testing, Relational Databases, JUnit, Mockito, Ubuntu, Bash Script, GitOps, DevOps Engineer, REST, Infrastructure as Code (IaC), Distributed Systems, Apache, Apache Spark, Apache Beam, Jest, Real-time Streaming, Apache Druid, Redis

Senior Full-stack Engineer

2017 - 2018

Avocarrot (Glispa Global Group)

Maintained and implemented new features on Avocarrot, a leading ad exchange network with hundreds of clients and systems handling thousands of requests per second.
Worked as a full-stack engineer, implementing web applications with Node.js and Java on the back end and Angular and Ember.js on the front end.
Served as a data engineer and built ETL processes in Python and Scala, powering internal and external reporting and billing.
Contributed to the Dockerization and migration of the whole stack of more than 20 microservices to Kubernetes.

Technologies: Amazon Web Services (AWS), Ansible, Apache Kafka, BigQuery, Node.js, Ember.js, Apache Spark, Spark, Docker, Kubernetes, Java, Druid.io, Apache Airflow, GitLab, GitLab CI/CD, Git, Hadoop, Python, Scala, Data Engineering, Back-end, CI/CD Pipelines, ETL, Data Pipelines, DevOps, Continuous Integration (CI), Continuous Delivery (CD), GitHub, Monitoring, Systems Monitoring, Unit Testing, Agile, Full-stack, API Connectors, REST APIs, Microservices, APIs, OpenAPI, Data Architecture, Big Data, Data Warehousing, Software Development, Relational Databases, JUnit, Mockito, Ubuntu, Bash Script, REST, Distributed Systems, Apache, Jest, Amazon DynamoDB, Apache Druid, Redis

Full-stack Engineer | Technical Lead

2014 - 2017

Project Beagle (FTI group)

Led a team of highly skilled engineers to build an automated bed bank for one of the largest tour operators in the world.
Served as a core member in the team that implemented the high throughput and low latency search engine built with microservices in Java Spring and Scala for hotel room availability and prices.
Wrote and optimized SQL queries to achieve lower latency.
Built new products in AngularJS and Angular 2 as a front-end engineer.
Served as a scrum master, helping the team overcome obstacles and facilitating the Scrum methodology throughout the company.
Acted as a product owner and communicated with business clients, clarifying requirements to be implemented before handing them over to the development team.
Wrote many end-to-end tests, helping to automate the process of testing and reduce the possibility of releasing bugs to production.
Helped the company embrace a DevOps mindset, transitioning from a fixed-release cycle to continuous deployment so that features could get shipped to production faster.

Technologies: Slack, IntelliJ IDEA, Continuous Integration (CI), Architecture, GitLab, Jira, Linux, Scala, Apache Cassandra, Spring, Continuous Deployment, DevOps, JavaScript, Scrum, Git, SQL, RabbitMQ, Docker, Cassandra, PostgreSQL, MySQL, CSS, HTML, Angular, Hibernate, Java, Back-end, Spring Boot, CI/CD Pipelines, Akka, Continuous Delivery (CD), GitHub, Monitoring, SonarQube, Unit Testing, Agile, Full-stack, REST APIs, PostgREST, Microservices, APIs, Hospitality, Software Development, Integration Testing, Relational Databases, JUnit, Mockito, Ubuntu, Bash Script, GitOps, DevOps Engineer, REST, Infrastructure as Code (IaC), HBase, Apache

SAP Developer

2011 - 2014

Step One Consulting SA

Worked on the end-to-end material management and warehouse management implementations for large Greek and international companies.
Connected two SAP systems from different companies to achieve electronic invoicing (e-invoicing).
Designed and implemented a mobile sales app for sales representatives to be able to complete orders remotely.

Technologies: ABAP, SAP, Software Development

Experience

Updoc Health-tracking App for Android and iOS

A hybrid app designed to help users keep track of their symptoms and other health-related information. I was in charge of taking an idea and converting it into a product, which included various tasks, ranging from talking to clients and designing a product that meets their needs to solving the UI/UX problems to implementing the front-end and back-end layers of the application. The app was based on Ionic, an Angular framework supporting mobile apps, and Firebase.

[Open-source Contribution] Apache Airflow

https://github.com/apache/airflow/pull/7127

Airflow is a sophisticated scheduler for workflows and is commonly used for scheduling data pipelines. My contribution to the project was solving a bug regarding the Druid operator, which is used for submitting tasks to Druid.

[Open-source Contribution] Kafka Connect

https://github.com/confluentinc/kafka-connect-hdfs/pull/283

Kafka Connect is a framework for connecting Kafka with external systems, such as databases and file systems. One of the sinks provided is HDFS, and my contribution was adding support to write records from Kafka to HDFS in a plain string format.

Education

2012 - 2017

Master's Degree in Computer Science and Engineering

University of Patras - Patras, Greece

2004 - 2010

Bachelor's Degree in Computer Engineering and Informatics

University of Patras - Patras, Greece

Certifications

FEBRUARY 2016 - PRESENT

Functional Programming Principles in Scala

Coursera

APRIL 2012 - PRESENT

Machine Learning

Coursera

Skills

Libraries/APIs

REST APIs, Node.js, OpenAPI, React, NgRx, PostgREST

Tools

Git, GitHub, Apache Druid, Cloud Dataflow, SonarQube, Apache, Apache Beam, Ansible, IntelliJ IDEA, WebStorm, Slack, Jira, GitLab, RabbitMQ, BigQuery, Apache Airflow, GitLab CI/CD, Confluence, Google Kubernetes Engine (GKE), Amazon EKS, Jenkins, AWS CodeBuild, Kafka Streams, Amazon Simple Queue Service (SQS), Amazon Simple Notification Service (SNS), Terraform

Languages

Java, SQL, Java 11, Bash Script, JavaScript, TypeScript, Scala, HTML, ABAP, Python, PHP, CSS

Frameworks

Spring, Angular, JUnit, Mockito, Vert.x, Hibernate, Ionic, Spark, Apache Spark, Spring Boot, Hadoop, Ember.js, Akka, Jest

Paradigms

Scrum, Continuous Delivery (CD), Unit Testing, Agile, Microservices, REST, DevOps, Continuous Integration (CI), Continuous Deployment, ETL

Platforms

Docker, Apache Kafka, Firebase, Kubernetes, Linux, Amazon Web Services (AWS), Google Cloud Platform (GCP), Ubuntu, Oracle, MacOS, Oracle Database, AWS Lambda, Azure

Storage

MySQL, PostgreSQL, Relational Databases, Druid.io, MongoDB, NoSQL, Data Pipelines, Cassandra, Google Bigtable, BigTable, HBase, Amazon DynamoDB, Redis

Industry Expertise

Healthcare

Other

Google BigQuery, Back-end, Full-stack, APIs, Software Development, Integration Testing, Architecture, Data Engineering, CI/CD Pipelines, Metabase, Monitoring, Systems Monitoring, Hospitality, Data Architecture, Big Data, Data Warehousing, Cloud Architecture, GitOps, DevOps Engineer, Infrastructure as Code (IaC), Distributed Systems, Apache Cassandra, SAP, API Connectors, Lambda Functions, Stream Processing, Real-time Streaming, Google Cloud Build, GitHub Actions, Google Cloud Dataflow

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