---
title: "Marcin Jasion"
description: "I am a passionate Platform Engineer with 12 years of experience. I have a deep understanding of application and infrastructure architecture, and the software development lifecycle. As a problem solver, I am always eager to find new and innovative solutions to complex challenges."
canonical: https://mjasion.pl/
---

# Marcin Jasion

Senior Platform Engineer.

I am a passionate Platform Engineer with 12 years of experience. I have a deep understanding of application and infrastructure architecture, and the software development lifecycle. As a problem solver, I am always eager to find new and innovative solutions to complex challenges.

## Links

- [About](https://mjasion.pl/about/)
- [Archives](https://mjasion.pl/archives/)
- [Tags](https://mjasion.pl/tags/)
- [RSS / Atom feed](https://mjasion.pl/index.xml)
- [Sitemap](https://mjasion.pl/sitemap-index.xml)

## Latest Posts

- 2026-05-25 — [Two Agents, One MCP Server: Using a Second Claude as a Harness for the First](https://mjasion.pl/posts/development/two-agents-one-mcp-harness/) (development) — How to test AI-generated code: a differential-testing pattern over MCP. One agent built my Polish tax calculator and exposed it over MCP. A second Claude Code agent, with no shared context, audited the math against raw broker data and found real bugs. This is what harness engineering looks like in practice.
- 2026-02-25 — [Why I'm Choosing Cloudflare and TanStack for My Side Projects](https://mjasion.pl/posts/development/why-i-chose-cloudflare-and-tanstack/) (development) — After building with Vercel and Supabase, I switched to Cloudflare and TanStack. Here's why - and what I gained.
- 2023-06-25 — [Implementing Leader Election in Golang using Kubernetes API](https://mjasion.pl/posts/kubernetes/implementing-leader-election-in-go-using-kubernetes-api/) (kubernetes) — Learn how to implement a leader election mechanism in Golang using the Kubernetes API, leveraging lease locks and distributed coordination to ensure reliable task execution in distributed systems.
- 2022-06-29 — [How to setup AWS Site-to-Site VPN with Unifi UDM 🔒](https://mjasion.pl/posts/cloud/how-to-setup-aws-site-to-site-vpn-with-unifi-udm/) (cloud) — Site-to-Site VPN allows connecting local network with AWS VPC. This blog is a step-by-step instruction to establish connection
- 2022-06-14 — [How to configure parallelism in HCP Terraform](https://mjasion.pl/posts/cloud/how-to-set-parallelism-in-terraform-cloud/) (cloud) — Speed up terraform plan and apply 4x in HCP Terraform. Configure TFE_PARALLELISM or per-stage TF_CLI_ARGS_plan/apply via workspace variable sets.
- 2022-06-10 — [How to enable debug and trace logs in HCP Terraform and Terraform Enterprise](https://mjasion.pl/posts/cloud/how-to-enable-debug-in-terraform-cloud/) (cloud) — Enable TF_LOG=TRACE/DEBUG in HCP Terraform and Terraform Enterprise remote runs via workspace variables. Includes local execution fallback for fast iteration.
- 2022-04-25 — [How to debug Istio Upstream Reset 502 UPE (old 503 UC)](https://mjasion.pl/posts/kubernetes/how-to-debug-istio-upstream-reset/) (kubernetes) — Fix Istio 502 UPE upstream_reset_before_response_started{protocol_error} errors. Real debug walkthrough using Envoy logs, Wireshark, and ksniff.
- 2022-04-09 — [Deploy your first blockchain contract to Ethereum](https://mjasion.pl/posts/development/first-blockchain-contract/) (development) — Step by step guide to deploy first contract on Ethereum blockchain
- 2020-04-17 — [How to label GitLab notification in Gmail by headers?](https://mjasion.pl/posts/development/label-gitlab-notifications/) (development) — You can label emails by headers in Gmail. To do this you have to create a script that periodically scans for new emails in your inbox. To demonstrate it I will use Gitlab notifications and we will add labels to messages basing on their headers