I attended HackIllinois held on Feb 27th, 2026, where Modal was a sponsor with a dedicated track.
We built **HackBitz,** one autonomous agent per habit you want to track and get better at. We used Modal to deploy Telegram webhooks, cron jobs, a vLLM on a GPU container for inference. A lot learned in the chaotic 36 hours.
While the hackathon was over, as a frontend engineer I couldn't ignore how performant and smooth the dashboard felt while building our project. I had to know at least some of the recipe behind it.
I kept DevTools open and started navigating across the dashboard.
swr.ts initiated everythingAlmost every API call traced back to one file: swr.ts. One file, orchestrating all the polling, revalidation, and deduplication across the entire dashboard.
I checked the Sources tab on a hunch, half expecting minified garbage. As the source maps was enabled, I could read the entire client side source code. Found a Chrome extension that downloads the entire codebase with folder structure intact, and that was my week sorted.
Going through the client-side source gave me a pretty good picture of how useSWR was designed to abstract away the complexity.
Alongside it, useInViewport worked together with useSWR to gate API calls to only visible components, which was a really smart pairing.
Observations I found worth noting :
useSWR: light weight custom hook implemented in ~300 lines, no library dependency, minimal but exactly enough.priority: 'low' on fetch calls to yield to bundle downloads during page navigationAbortController with a captured closure variable, this took me multiple re-reads to get a clear idea, i found it to be a great example of leveraging closures.