jguillaumesio

Engineering, explained
as I ship it

Notes from real production work, payments, AI agents, architecture, and why each decision was made.

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ai ·

A reader read my benchmark better than I did

I published a fine-tune that beat prompting by 29 points. A commenter said the gap between my two accuracy drops was the real signal. He was right that my table was misleading, wrong about which arm was inflated, and the experiments I ran to check produced a third answer.

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prod-ops · gdpr ·

The client wanted production data in preprod. I said no, then gave them something better.

A reasonable request from a reasonable client: make preprod look like prod, with real data. Why that would have been the worst security decision in the project, how I pushed back without a fight, and the anonymised seed pipeline that made preprod more useful than a copy would have been.

prod-ops · security ·

The certificate expired in silence, and the scans never stopped

A renewal cron ran every night for months and never renewed anything, because of one wrong letter. Meanwhile the server took thousands of scans and brute-force attempts a day. Here is what CrowdSec actually blocked, the nginx rules that held, the ports I should never have exposed, and why Cloudflare is the next layer.

Users emailed me about 500s before I ever saw them prod-ops I was grepping JSON over SSH while production was down prod-ops The Friday push that taught me to ban commits on main prod-ops My fine-tuned model scored 100%. The benchmark was lying. ai Database backups that actually restore: the pgdata I lost prod-ops PII and data masking: how to stop leaking personal data everywhere gdpr GDPR data retention and deletion: a practical guide for developers gdpr CPU utilization lies: autoscaling a single-threaded service cloud-ops Docker never restarted my database: the price of restart: no prod-ops The tests were already written. Nothing ever ran them. prod-ops Docker bypassed my firewall: the database port was open to the internet prod-ops The MCP servers that actually earn their keep with Claude Code ai The docker build that filled the disk and took down production prod-ops Shipping a SaaS on one VPS with Docker Compose: an honest audit prod-ops Sharing a Claude Code config across a team ai A practical playbook for running a remote dev team team The cart timer expired while they were paying. Now what? webdev Multiple accounts in Claude Code: the complete setup ai Cloudflare under the hood: how it works and how attackers try to get around it cloudflare Stop refunding payments you should never have charged webdev Sharing cookies across subdomains locally cookies Architecture matters more than clean code architecture Debugging is more important than features devops Why the perfect code is less maintainable architecture Stripe alternatives in the EU webdev Social previews in React: UA detection webdev AI-powered git branch diff summaries devtools Testing Lambda + EventBridge locally devops AI infrastructure: a maintenance nightmare devops How to check your AI's actual context window ai Token economy: cutting context waste ai