Other have already explained, but to simplify, a tag-based media archive. The original is Danbooru (cardboard), an anime-based one (including NSFW, so I haven't linked). They often tend to be fandom-based.

A high-quality safe-for-work example of a standard online booru is Find A Fox.

OP's tool is a local single-user booru instead, using Hydrus Network as an example. Personally, I like its UI, and while it has a developer-driven swiss-army knife design vibe, I still like it and have used a wide range of its many options. I haven't tried Blombooru and can't see many screenshot samples so I can't assume what specific issues OP has and how Blombooru solved them.

it's like an otaku software were people upload artwork and other stuff, in theory you could store any kind of image or videos, and it is tag based.

no, the author is mr blomblo, hence the name!

ive imported around 2000 images, and it didn't take much, also take into account i only have 8gb of ram, so it did pretty well and pretty fast. first it crashed a few times but because i had a 300mb gif and it tried to read it and crashed. i have around 5000 images more but ill import them in batches because those are relatively organized in folders so it'll be easier to add tags as i go than dump everything and figure out what do to with them later. so far i dont notice any lag with my collection, during import it may take a bit more if your collection is larger tho but if you also have more ram... it also has Redis as an option for caching, i havent used it tho

My hydrus collection is 1.9TB with nearly 1m files. Can't say I've ever had any kind of slowdown. A search with 24.8k results takes about 5 seconds, and that's with the media stored on a HDD (though the database is on a SATA3 SSD). And run by an 8 year old AMD Ryzen 7 2700X. Plenty fast enough for me at least.