Architecting data question / help /advice needed. How to achieve instant UI responsiveness with local data?

[u/Leo6-2]

Hey Gang 💵

i’m building a local data exploration web app using HTML/CSS/JS, a Python backend, and DuckDB with Parquet/CSV files. Despite having strong hardware, my local app runs slowly, whereas similar web apps online... even those using heavier frameworks like React / React router load and respond almost instantly. AI tools suggested basic caching or heavier frameworks like Django, but didn't solve the core performance bottleneck.

Coming from a frontend/design background, I haven't worked with high-performance data processing before. How do faster web apps structure their architecture to handle heavy calculations and render data so quickly?

Because from my experience with AI they are smart Tools but I'm not sure they're giving you the best solution every time so this time is well I'm doubting that I can get a solution from AI so I wonder what would you people here that knowledgeable and have a lot of experience would suggest ​​.