Fls-na.amazon.com: Top Blocked Domain

I’ve installed a Pi-Hole recently and 77% of queries are being blocked. Nearly all of them are from fls-na.amazon.com. I have no idea what that domain is. I’ve a heavy Amazon user and haven’t yet noticed anything not working. Should I whitelist that domain?

Thanks

According to my quick research,

Searching for fls-na.amazon.com

Found In EasyList-Lithuania. Matching Included:
fls-na-amazon.com
fls-na.amazon.com

Found In GandJ-Hosts. Matching Included:
fls-na-amazon.com

Found In KowabitBOD. Matching Included:
fls-na.amazon.com

Found In Mat1th-DNS-add-block. Matching Included:
fls-na-amazon.com
fls-na.amazon.com

Found In Michael-Trimms-Hosts. Matching Included:
fls-na.amazon.com

Found In Mother-of-All-ADBLOCKING. Matching Included:
fls-na.amazon.com

Found In Notracking-hostnames. Matching Included:
fls-na.amazon.com

Found In Steven-Blacks-Fakenews. Matching Included:
fls-na.amazon.com

Found In Steven-Blacks-Gambling. Matching Included:
fls-na.amazon.com

Found In Steven-Blacks-Porn. Matching Included:
fls-na.amazon.com

Found In Steven-Blacks-Unified-Hosts. Matching Included:
fls-na.amazon.com

I learned that fls-na.amazon.com is resulting from my installation of the Amazon Chrome extension. As soon as I remove the extension, no more requests for fls-na.amazon.com.

It seems that blocking this domain means the IMDB App stops working to a very large degree.

If I just try going to the domain from a (piholed) machine browser I get this response

[ERROR]: Unable to parse results from queryads.php: Connection timeout (3s)

Not sure if that is why any valid data may not be getting through.

I believe this address fls-na.amazon.com, is used for authenticating apps “purchased” (paid or free) from the Amazon App store.
With it blocked the Plex Amazon App puts me in “Trial Mode”, and is virtually unusable, but after whitelisting the address it validates my purchase just fine.
I would guess that it shows up in so many lists due to some Apps that use bad/malicious ads, but also authenticate purchases through the Amazon App store. Given that it’s an Amazon domain, I’m pretty sure it’s (mostly) safe from malware, and likely not the direct source of ads.

Other similar, and unblocked, Amazon addresses are:
mas-ext.amazon.com
mas-sdk.amazon.com
mas-ssr.amazon.com
After some googling it seems the ‘mas’ is the “Mobile Associates API”, where ‘ext’ is for in-app purchases (like Movies in Amazon Video), ‘sdk’ seems related to the API itself. The ‘ssr’ seems to be related to the App Store itself, but I’m not sure how.