Luciano Mammino 📙 Node.js Design Patterns

What if your AWS containers could start 10× faster without changing your code? 👀 Eoin and I ran 1,320 ECS task executions to find out. Spoiler: SOCI lazy loading is seriously impressive, especially with large images. Also, #AWS Bites #podcast is BACK! 🎙️

Big update to Crafting Lambda Functions in Rust! 🦀🚀 Chapter 10 is out: Tower-powered middleware for AWS Lambda. Think tracing, error handling, headers and rate limiting, without the boilerplate in every handler. And there's a brand-new cover! 🎨🏔️

We go from Tower's Service and Layer to a DynamoDB-backed rate limiter and reusable observability middleware. Plus 2 new appendices: Axum on Lambda, and CI/CD with GitHub Actions, OIDC & AWS SAM. 10 of 11 chapters done! 🏁

I've used #Docker for 10+ years and I thought I knew how image layers work. Then I asked one innocent question: if layers are just tar archives stacked on top of each other, how can a layer DELETE a file from a previous one? 🧵 loige.co/hidden-desig...

... Also my docker captain friends might like this (...or tell me I am an idiot for not knowing earlier 🫡) @gianarb.it @francescociulla.bsky.social

I've used #Docker for 10+ years and I thought I knew how image layers work. Then I asked one innocent question: if layers are just tar archives stacked on top of each other, how can a layer DELETE a file from a previous one? 🧵 loige.co/hidden-desig...

All the experiments are reproducible, with scripts, raw logs and the full version matrix: github.com/lmammino/bro...

I've used #Docker for 10+ years and I thought I knew how image layers work. Then I asked one innocent question: if layers are just tar archives stacked on top of each other, how can a layer DELETE a file from a previous one? 🧵 loige.co/hidden-desig...

Which raises the obvious question: what if my file is literally called .wh.foo? Linux is fine with it. OCI layers can't represent it. So of course I tried it with BuildKit... 🧪 It builds. It runs. It works on my machine. Then you push it, and foo disappears everywhere else 🙃

I've used #Docker for 10+ years and I thought I knew how image layers work. Then I asked one innocent question: if layers are just tar archives stacked on top of each other, how can a layer DELETE a file from a previous one? 🧵 loige.co/hidden-desig...

Tar can say "here's a file". It can say "here's a new version of that file". But it has no way to say "remove this file from the archive below me". So the OCI image spec has a trick: to delete foo, a later layer ships an entry called .wh.foo 🫥

⚡️ 🐢🚀 Node.js QUIZ 🐢🚀 ⚡️ ``` FEATURE_ENABLED=false node app.js ``` Then, in app.js: ``` if (process.env.FEATURE_ENABLED) { console.log('feature on') } ``` What gets printed? 🤨

NODE_ENV=production does not make your app faster by itself. It's a convention, not a Node.js feature. It just tells your dependencies (Express, React, bundlers) to behave like production. If they don't check it, nothing changes.

⚡️ 🐢🚀 Node.js QUIZ 🐢🚀 ⚡️ ``` FEATURE_ENABLED=false node app.js ``` Then, in app.js: ``` if (process.env.FEATURE_ENABLED) { console.log('feature on') } ``` What gets printed? 🤨

Now the uncomfortable part: env vars are a mediocre home for secrets. - child processes inherit them by default - they show up in docker inspect - readable from /proc/PID/environ - crash reporters love to capture the whole environment Prefer a secrets manager in production.

⚡️ 🐢🚀 Node.js QUIZ 🐢🚀 ⚡️ ``` FEATURE_ENABLED=false node app.js ``` Then, in app.js: ``` if (process.env.FEATURE_ENABLED) { console.log('feature on') } ``` What gets printed? 🤨

It layers nicely too: node --env-file=.env --env-file=.env.local app.js Later files win. And since 22.9 there's --env-file-if-exists for optional files. One gotcha: OS variables always beat the .env file. The file provides defaults, it never overrides.

⚡️ 🐢🚀 Node.js QUIZ 🐢🚀 ⚡️ ``` FEATURE_ENABLED=false node app.js ``` Then, in app.js: ``` if (process.env.FEATURE_ENABLED) { console.log('feature on') } ``` What gets printed? 🤨

The "false" trap: FEATURE_ENABLED=false node app.js if (process.env.FEATURE_ENABLED) { // this runs 😱 } "false" is a non-empty string, so it's truthy. Always compare explicitly: process.env.FEATURE_ENABLED === 'true'

⚡️ 🐢🚀 Node.js QUIZ 🐢🚀 ⚡️ ``` FEATURE_ENABLED=false node app.js ``` Then, in app.js: ``` if (process.env.FEATURE_ENABLED) { console.log('feature on') } ``` What gets printed? 🤨

Environment variables in Node.js look trivial until they bite you: everything is a string, "false" is truthy, and every child process you spawn inherits your secrets. I just published a complete guide. Here's the short version 🧵

⚡️ 🐢🚀 Node.js QUIZ 🐢🚀 ⚡️ ``` FEATURE_ENABLED=false node app.js ``` Then, in app.js: ``` if (process.env.FEATURE_ENABLED) { console.log('feature on') } ``` What gets printed? 🤨

🎉 Big news: Node.js is changing its release schedule for the first time in 10 years. From October 2026, less to remember and easier to know what's Current or LTS. Here's everything you need to know 🧵👇

♻️ Every release becomes LTS. No more "wait, is it odd or even?" 🙃 🧪 A new Alpha channel (27.0.0-alpha.1) gives library authors a 6-month window to test breaking changes early.

🎉 Big news: Node.js is changing its release schedule for the first time in 10 years. From October 2026, less to remember and easier to know what's Current or LTS. Here's everything you need to know 🧵👇

Node.js 26 shipped this week 🎉 My birthday is close, so I'm officially calling it an early birthday present from the Node.js team. 😂 This release doesn't look flashy at first glance, but the additions are genuinely useful in everyday code. I wrote a code-heavy tour, here's what stood out 🧵

Plus the cleanup: private _stream_* modules, writeHeader(), and --experimental-transform-types are all gone. module.register() is runtime-deprecated. If you maintain libraries, this is a good time to grep for those.

Node.js 26 shipped this week 🎉 My birthday is close, so I'm officially calling it an early birthday present from the Node.js team. 😂 This release doesn't look flashy at first glance, but the additions are genuinely useful in everyday code. I wrote a code-heavy tour, here's what stood out 🧵

Iterator.concat() composes lazy iterables into a single iterable without ever materializing intermediate arrays. One catch though: it's sync-only. For async iterables you'll need a small concatAsync helper, and the article includes a one-liner you can paste in.

Node.js 26 shipped this week 🎉 My birthday is close, so I'm officially calling it an early birthday present from the Node.js team. 😂 This release doesn't look flashy at first glance, but the additions are genuinely useful in everyday code. I wrote a code-heavy tour, here's what stood out 🧵

Temporal is finally stable and enabled by default. You can drop Moment.js / Luxon / date-fns. The global Temporal handles dates, time zones, and DST math correctly out of the box. If you've ever shipped a "remind me in one day" feature that drifted by an hour twice a year, this is for you.