02 — Case study · Side system · Saturn
Growfin Newsletter
Fully automated bi-weekly fintech intelligence brief — 13 sources researched, written, evaluated and delivered to subscribers without a human in the loop.
Year
2025 — ongoing
Role
Designer & operator of the whole system
Context
Side system
Stack
n8n · Claude API · Langfuse · Promptfoo · Brevo · Notion
13
sources monitored
6
editorial sections per issue
0
humans in the loop
The challenge
Staying sharp on fintech means hours of reading every week — funding rounds, product launches, regulation. I wanted the output of that reading without the hours, at an editorial quality I'd be willing to put my name on, delivered on a schedule whether I'm busy or not.
What I built
- An n8n pipeline pulling from 13 curated sources, deduplicating and scoring items for relevance.
- A Claude-powered editorial layer writing six structured sections per issue, with a consistent voice defined in the system prompt.
- Langfuse tracing on every generation — each issue's cost, latency and outputs are observable, not a black box.
- Promptfoo evals guarding the prompts: changes ship only if they beat the previous version on the test set.
- Brevo for scheduled delivery to the subscriber list, Notion as the permanent archive.
Results
- The brief ships every two weeks with zero manual intervention — research, writing, QA and delivery are all systematized.
- A real LLM-ops setup (tracing + evals) on a personal project, the same discipline used on production systems.