Hans Drost

Stack:

Scala (2.13.16), ZIO (2.1.19, kafka, config, logging, sqs), Tapir, scalacheck,

cats (org.typelevel), GRPC / protoc / protobuf, org.apache.kafka, io.circe,

Doobie, Flyway, react.js, Spring Cloud Config, Cucumber, Docker,

ElasticSearch, Axon Framework, Kibana, Microservice development,

Functional Programming, Scrum / Lean and agile principles, Behaviour

Driven Development (BDD), Test Driven Development (TDD), CI / CD,

DevOps, AWS (Dynamo DB, S3, SQS), Kubernetes, Argo CD, MySQL,

DB2, H2

Contribution:

Aimwel has a SaaS platform for job advertising with which

job boards, publishers, and advertisers distribute job campaigns

automatically to (inter)national advertising channels. The

platform wanted to scale quickly from a handful of channels to a broad

network with partners such as LinkedIn, Meta, Criteo, Adzuna, and other

aggregators. Each new advertising channel required customization, making the

growth of the network directly dependent on the capacity of the

development team.

My assignment: ensure that new advertising channels could be added quickly

without impacting existing services. Specifically, I built:

• the central PSA backend with command and event handling (Axon),

including gRPC and REST interfaces for external clients;

• distribution services for advertising channels such as LinkedIn, Meta,

Criteo, RTBHouse, talent.com, and Adzuna;

• automated feed processing for XML and JSON

job feeds (fetching, validation, transformation, and asynchronous

processing);

• an expense reconciliation service for automatic comparison of

actual click prices with budgets;

• the central configuration service for backend and

frontend components;

• shared libraries for models, configuration, exception handling, and

utilities.

Aimwel could onboard new advertising channels significantly faster —

without changes to existing channels posing a risk. The architecture remained

stable as the network grew.

Stack: Scala (v2.12.6), Cats (for Scala), react.js, Polymer, Twitter Bootstrap, JavaScript, scalikejdbc, PHP, Akka (HTTP, Stream, Actor, gRPC), Play Framework (for Scala), ScalaTest, Cucumber, Docker, ElasticSearch, Quartz Job Scheduler, Axon Framework, Kibana, Kubernetes, Microservice development, Scrum / Lean and agile principles, Behaviour Driven Development (BDD), Test Driven Development (TDD), CI / CD, DevOps, Domain Driven Design (DDD), Functional Programming, AWS (Dynamo DB, Kinesis, S3, SQS, Route 53), MySQL, H2, MongoDB, Redis

Contribution:

DPG Media Employment Solutions manages platforms like Intermediair and

Nationale Vacaturebank — which help thousands of job seekers daily and

support organizations in attracting talent. Thousands of job postings and millions of data points are processed daily. The underlying job posting processing was based on

SanDiego, a legacy application that was no longer supported by the vendor. Every adjustment took disproportionately much time, making the platform a brake on innovation rather than a driver of renewal.

My assignment: contribute to the New Development Platform (NDP) — the

microservices platform that was to phase out SanDiego, allowing DPG Media to independently further develop its job posting platforms again. Specifically, I built:

• design and build backend services in Scala and Akka;

• model and process events within an event-driven

architecture (Axon event sourcing);

• develop microservices for job posting processing and Salesforce

integrations;

• integrate external services and data streams;

• set up CI/CD pipelines and release to Kubernetes.

Intermediair and Nationale Vacaturebank have since been running on a

scalable, manageable infrastructure. DPG Media could again develop its

job posting platforms faster — without every adjustment becoming a major project.

Stack: Java (v1.8), JavaScript, Spring (Boot, Core, AOP, WS), Aspect Oriented

Programming (AOP), AngularJS 2.0, Angular CLI, Protractor, Karma,

Selenium, Cucumber, Scrum / Lean and agile principles, Behaviour Driven

Development (BDD), Test Driven Development (TDD), Apache Tomcat,

Atlassian Bitbucket, Atlassian Bamboo

Contribution:

NS OVEasy offered consumers access to public transport-related

services via a single platform — from subscriptions to reimbursements. The backend consisted of multiple standalone services that had grown without clear coherence, requiring more coordination for further development each time than necessary.

My assignment: stabilize and expand the backend — and enable the team to do so themselves in the future. Specifically:

• manage and further develop existing microservices;

• build new backend services with Spring Boot and Spring Cloud;

• set up a proof-of-concept with Spring Boot Admin and Eureka

for service monitoring;

• provide technical guidance to team members on Java, architecture, and

design choices.

For the first time, the team had direct insight into the health of the

individual services. Team members could subsequently justify architectural choices more independently — NS could develop the service provision on OVEasy with more certainty.