account_sequence and suggested_fee in substrate

Question

I am looking into rosetta-api for substrate. I have two questions regarding one of its endpoint construction/metadata

• Does substrate maintain an account_sequence number somewhere? where can I find it?
• How can I calculate suggested fee. I guess the idea is max generated fee where acc balance should be more than that.

Reference

Answer 1

If for account sequence you mean the nonce of the account (number of outgoing transactions from the account), it is stored in the system account info together with other account data like free and reserved balances. You can query it via the rpc.system.accountNextIndex RPC method.

More interestingly, you can achieve both of your points with API Sidecar, which by the way, Rosetta based its implementation on:

• For the nonce (account sequence) and the rest of the account info, you can use the GET accounts/{account-id}/balance-info endpoint.
• For the suggested fee, you can use the POST transaction/fee-estimate endpoint with the transaction payload as the request body.

Here you have a complete list of endpoints for API Sidecar.