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Achievements

Achievement: Pull Sharkx4Achievement: Pair Extraordinairex3Achievement: QuickdrawAchievement: YOLOAchievement: Arctic Code Vault ContributorAchievement: Starstruck

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chrj/README.md

Hi, I'm Christian 👋

Lead Software Engineer on the Email Platforms team at Klaviyo. I have more than 20 years of experience in backend development, distributed systems, databases, systems operations, and networking. I also led teams for SaaS, AI/ML, and data platforms. I live in Boston, MA.

  • 🔭 Now: at Klaviyo, I build the systems that deliver email reliably at high volume
  • 🛠 Before: Director of Engineering at DataRobot (MLOps and Governance), CTO and co-founder of Ubivox (newsletter platform)
  • 🌱 My spare-time projects are about SMTP, DNS, and networking. See the list below
  • 📫 christian@technobabble.dk · linkedin.com/in/joergensen · technobabble.dk

Languages and tools

Go Rust Python JavaScript Kubernetes PostgreSQL WireGuard

Things I maintain

These are hobby projects outside of work, for fun.

Conduit: a self-hosted gateway from email to webhook, built on smtpd. Conduit converts inbound mail into an HTTP POST request. The response from the webhook maps to an SMTP status code. Then the remote mail server does its own retries.

ZeroDrop: free uptime monitoring from multiple locations. A control plane in Go controls distributed agents over a WireGuard mesh. The agents test HTTP, TCP, and TLS. The agents must agree before ZeroDrop sends an alert.

Doctor Whois: a small single-page application and REST API with network and cryptography tools.

Package Description
smtpd Build SMTP servers with STARTTLS, authentication, XCLIENT, and HELO/RCPT/DATA checks
pflog Parse Postfix mail logs into Go structures
wgnet Build user-space services inside WireGuard VPNs
ssrf Prevent SSRF in http.Transport
keyrate Rate limiters with a key (per user, per IP), based on x/time/rate
diggity DNS health checker: delegation, TTLs, DNSSEC chain of trust, cross-server answers
vanguard Prometheus black-box exporter (HTTP/TCP/SSH/SMTP) that operates over WireGuard
ircbot Asynchronous IRC bot framework for Rust, built on Tokio and proc macros
dmarc-report-parser Parse DMARC aggregate feedback reports (Rust library and CLI)
prometheus-dnssec-exporter Monitor DNSSEC and RRSIG expiration
prometheus-ssl-exporter Monitor SSL certificate expiration and connectivity

More at technobabble.dk.

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  1. smtpd smtpd Public

    Go SMTP server library

    Go 77 38

  2. wgnet wgnet Public

    wgnet provides a thin frontend for user-space VPN connections using the Go WireGuard implementation running on the gVisor user-space network stack.

    Go 1

  3. pflog pflog Public

    Postfix log parser for Go

    Go

  4. keyrate keyrate Public

    Wrapper around /x/time/rate to support per-key rate limits (for example per-IP or per-user)

    Go

  5. ssrf ssrf Public

    An SSRF validator for http.Transport

    Go

  6. dmarc-report-parser dmarc-report-parser Public

    DMARC aggregate report parser

    Rust 1