Contact

• E-Mail: contact@david.krentzlin.me
• Website: https://david.krentzlin.me
• GitHub: https://github.com/certainty

Summary

I’m a software engineer with management experience, and I thrive in environments which require technical expertise as well as good communication and leadership.

In my roughly 20 years as a software engineer, I have worked on multiple high traffic, distributed services in all stages of their life-cycles, in multiple domains, and helped to scale them operationally and organizationally.

I care about good culture and try to increase my understanding of the environments, teams, systems, values, and practices that enable organizations to sustain in an industry, that is fast-paced and requires constant feedback and learning.

Experience

Senior Software Architect — New Work SE [Jan 2023 - Present]

Developer Experience and Automation (Jan 2024 - Present)

As part of the ongoing cloud migration, I changed my area of responsibility so that I can support the organization best to move critical infrastructure into the cloud. In the developer experience and automation team I am a subject matter expert for the API infrastructure that powers the data needs for all our applications.

This includes the synchronous data fetching layer via our GraphQL API federation layer as well as asynchronous service integration with messaging infrastructure based on RabbitMQ / AmazonMQ.

My primary responsibility is to ensure seamless operation of our infrastructure, before during and after the migration of application workloads to the cloud. This requires careful consideration, planning, coordination and execution to minimize disruption of product development teams.

Leveraged skills: AWS cloud services, Terraform, GraphQL, Scala, Ruby, Golang, project management, Software Architecture, leadership

Cloud Platform Team (2023 - Jan 2024)

The cloud platform team is part of the central business unit, which provides internal services and products to our engineering organization. This team is an integral part of the cloud move initiative, which aims to lift our production platform into the cloud and help teams to reap the benefits of cloud services.

• build a landing zone, that meets the organization’s needs for security, cost transparency and governance
• bootstrap the cloud center of excellence to connect all business units and accelerate the cloud move
• support and consult early adopters to move first workloads to the cloud

AWS cloud service, Terraform, Terragrunt, AWS CDK, Typescript, project management, leadership

Tech Lead at — Hive Technologies [Aug 2022 - Jan 2023]

As the tech lead in the delivery experience team, in a fast-growing startup, I worked closely with the product owner to shape upcoming features and help the team to deliver them. In my short time at Hive I invested most of my time in bringing the team up to speed with modern software development practices, identifying system boundaries and responsibilities as well as stabilizing 3rd party integrations.

• stabilize the client, that was used to communicate with 3rd party APIs. I optimized for success rate, resilience and observability
• shape the development process together with the team to move from a reactive mode of working into a proactive one

Ruby on Rails, distributed systems, APIs, agile methods, project management, architectural guidance

Team Lead Architecture — New Work SE [Mar 2020 - Jul 2022]

I lead a team of six software architects & software engineers in a newly created solution architecture area. As a platform team, we built and operate the central GraphQL API, which is used by 200+ engineers to build their products faster and more robust. As a former individual contributor in the team, I took on the leadership position and helped my engineers to be self-sustained, autonomous and achieve the team’s objectives.

• build the newly established team and foster good collaboration, team ownership and consistent delivery
• help to establish data-driven software delivery
• and continuous improvement processes for consulting and platform projects
• drive architectural decisions and give architectural guidance for the engineering organization
• enable my direct reports and support them in achieving their objectives and growing them in their functions
• facilitate decision-making, group learning and continuous improvement to help the team take ownership of their platform

leadership, management, communication, agile methods, coaching, project management, strategic decision-making, architectural guidance

Senior Software Engineer — New Work SE [Dec 2015 - Mar 2020]

XING One - GraphQL Gateway (2017 - 2020)

I was part of the core platform team that planned, designed, developed and rolled out the central GraphQL Gateway, which is called XING One. I accompanied the service through the early project phase, when it was scaled to the whole organization, and when it reached maturity. The platform is now used by 200+ product engineers to build their products in a largely autonomous way.

• improved data handling for mobile and web clients by providing a faster, safer and more robust way to fetch data using GraphQL
• planned and played an integral role in the development of bigger parts of the GraphQL service like file uploads, caching and logged-out support
• increased availability, resilience, and performance of the GraphQL service through systematic measurement, profiling, monitoring and implementation of the required changes
• built fast, secure, resilient and reliable HTTP level service-to-service communication
• created and carried out workshops to train engineers in GraphQL and Scala
• provided architectural guidance and support for product teams to learn how to leverage GraphQL the best for their domains

Scala (AKKA, Finagle, Sangria), Ruby (Rails, Sinatra), GraphQL, distributed systems, RESTful APIs, caching, rate limiting, AMQP, MySQL, HTTP, network, concurrency, communication, lateral leadership

XING Messenger End-to-End Encryption (2016 - 2017)

• planned, designed and documented the integration of a double-ratchet protocol for the XING messenger together with external crypto experts
• designed and developed the backend integration to bring end-to-end encryption to the XING Messenger
• coordinated work of mobile engineers, backend engineers and external experts to bring the required encryption knowledge into the team and enable the delivery of end-to-end encryption

Ruby (Rails, Sinatra), AMQP, Cryptography, MySQL, Network protocols

XING Messenger (2015 - 2016)

• introduced highly available, resilient and performant real-time update channel for the XING messenger
• designed and implemented RESTful APIs to enable new features on the XING messenger
• developed load testing component to verify and measure the real-time update channel of the XING messenger and conducted performance / load testing
• improved the quality of the code base by driving and supporting a software design shift that provided a better basis for the development of features

Ruby (Rails, Sinatra), Elixir (Phoenix, OTP), AMQP, Cryptography, MySQL, network programming, functional programming, software architecture, software design, coaching, lateral leadership

Senior Software Developer — OMCnet GmbH [2007 - Nov 2015]

• introduced a more reliable and capable version of E-Mail policy service to enforce policies on the MTA
• automated operations workflows and developed solutions to manage a fleet of dedicated and shared servers
• designed, planned, and operated high-available solutions for storage and web services
• developed web-based management interfaces for dedicated and shared hosting environments
• introduced continuous integration pipeline to speed up the delivery of features for internal products
• designed and implemented configuration as code with puppet

Ruby, C/C++, Perl, Puppet, Scheme, PostgresQL, MySQL, network protocols, operations

Software Developer — Claxx.net [2005 - 2007]

• built a fully automated layout engine to generate parts of a magazine with sport-statistical data, which eliminated the need for a lengthy manual layout process
• developed web-based Interface for external customers to leverage in-house sports data
• automated workflows in the production of a sports magazine

Ruby, PHP, C/C++, Scheme, MSSQL, SXML, Quark

Skills

• Technologies: GraphQL, APIs, Messaging, Dist. systems, Compilers & Interpreters, AWS Cloud
• Programming languages: Scala (3+ years), Ruby (10+ years), Common Lisp (3+ years), Typescript (1+ years)
• Soft: Communication, coaching, mentoring, leadership, project management, agile software delivery
• Languages: German (native), English (fluent), Icelandic (novice), Danish (novice)