Investing it in an index fund would be a retirement account, even if it's a taxable brokerage. If you want to use it in the next 1–5 years (say, for a nice vacation). then you want HYSA.

Okay gotcha... What about if you wanted to use the money in 5-10 years instead, would you still use a HYSA for it then?

Basically, I'm trying to get a feel for how best to use extra money towards medium-term goals

I'd put extra to principle on loans or it'd be invested in a taxable brokerage as you mentioned. I use my taxable brokerage acc as a savings account that will be used in a couple years.

5-10 years id invest

I’d just watch it and decide when to start pulling out of the market or maybe I don’t have to pull it out bc other windfalls met the goal for what the money was for

However you don’t mention other revolving sinking funds…

Car maintenance

House maintenance

Vacation

Are those covered by your regular budget?

ibonds are popular currently. 10k max annually.

Https://www.reddit.com/r/personalfinance/wiki/commontopics

Ok interesting...

So I don't have a car or a house, but I live in a very HCOL city. Vacation is one of the main things I want to save for going forward. I just upped my 401K contribution so in this new budget, I should have about $700 cash left per month that I'd like to put in sinking funds.

I think I want to avoid having 100% of my extra income tied up in the 401K because I want to .... live life lol so if there's a month where I actually have $1000 left over, I'd like it to go to good use

HYSA is where we have squirreled money away. We have easy access, no penalties and, currently, the rates are so high that we haven't found anything that competes.

I'd recommend reading the Prime Directive article from the wiki.

Okay gotcha... putting it in a HYSA would make me the most comfortable, but I wasn't sure what the recommendation was for small amounts of money specifically. It's not like I regularly get windfalls, but I do regularly have small amounts of money appear and I don't want it to go to waste!

We started out with just a few thousand but make regular contributions. We have a mutual fund, the emergency fund, 401k, Roth, stocks... out of all of it, the HYSA is the only one making money, the only one that is safe and the only one that won't penalize us if things were to nose dive and we needed our money.

Great way to put things in perspective, thank you!