What's the proper way to fetch a user's balance? (if not /accounts/<address>/resources

[Mouradif]

Discord user ID

0xSynon

Describe your question in detail.

It was my understanding that to fetch an address's coins balances, I had to hit the /accounts/<address>/resources endpoint of the Aptos Node API. It has worked for me so far on mainnet but almost a week ago, I sent some APT to this address on testnet: 0xb3ad6416320fede7866b22db0eebd4e9a630a143a14674a2244d933e097d8288. I was able to see the balance on the explorer but still

$ curl https://api.testnet.aptoslabs.com/v1/accounts/0xb3ad6416320fede7866b22db0eebd4e9a630a143a14674a2244d933e097d8288/resources
[]

Even more concerning yet:

$ curl https://api.testnet.aptoslabs.com/v1/accounts/0xb3ad6416320fede7866b22dbebd4e9a630a143a14674a2244d933e097d8288/transactions
{"message":"Account not found under address 0xb3ad6416320fede7866b22db0eebd4e9a630a143a14674a2244d933e097d8288","error_code":"resource_not_found","vm_error_code":null}

someone from the Aptos team answered me on the discord :

apt sent to the account is stored in a fungible store (which is an object owned by your account, https://explorer.aptoslabs.com/object/0xe521bacfe0e61c3eca8d62d7e0f8cfd5eaec693c95b6757453f99ac90cf3ac77/transactions?network=testnet)
your account resource is empty until there's data directly stored under your account

I'm not sure I understand but my key takeaway is that it is possible for an account to hold some APT and for the /resources endpoint to still return an empty array. Then what alternative method can I use to fetch the APT balance of an accoung knowing only that account's address?

Many thanks!

PS: Bonus question if someone can explain the fungible store object thing

[0x-j]

this page should expain the fa and fa store
https://aptos.dev/en/build/smart-contracts/fungible-asset

for getting apt balance, you can call this api https://aptos.dev/en/build/apis/fullnode-rest-api-reference#tag/accounts/GET/accounts/{address}/balance/{asset_type}

[Mouradif]

Thanks!