Is it possible to retrieve only a single variable from contract storage?

Question

As far as I can tell using the taquito npm package, in order to get any storage from a contract, you have to get all of a contract's storage. This seems like it can become highly inefficient if you are storing lots of data in a contract but I only needed to get a single variable.

I'm using Archetype lang to write my contracts.

Answer 1

Yes, that is possible with TzKT API (it's free and open-source), which allows you to specify a path to a particular part in the storage you want to receive.

For example, if a contract has the following storage:

{
    "vesting": {
        "vesting_schedule": {
            "next_payout": "2019-09-29T08:30:00Z",
            "payout_interval": "2629800"
        },
        "vesting_quantities": {
            "vested_balance": "162775594954",
            "vesting_increment": "199041301565"
        }
    },
    "key_info": {
        "key_groups": [
            {
                "signatories": [
                    "edpkvS5QFv7KRGfa3b87gg9DBpxSm3NpSwnjhUjNBQrRUUR66F7C9g",
                    "edpktm3zeGMzfzFuqgyYftt7uNyVRANTjrJCdU7bURwgGb9bRZwmJq",
                    "edpkucCnbeGPWNvGHeTQ5hENHPrc8txBBiQXNphu3jgv9KYbhQBovd",
                    "edpkuNjKKT48xBoT5asPrWdmuM1Yw8D93MwgFgVvtca8jb5pstzaCh"
                ],
                "group_threshold": "2"
            },
            {
                "signatories": [
                    "edpkukogJzCZSAfc5foRpEZGsryMjiXj77VxcFLzZoreB1vZWFeKc2",
                    "edpkuSZ1GoM6MALh4fPZBrwDhGwY9vENEoyctcXuDK3yoiX4xWhMaA",
                    "edpkvXL9B32DcEbMNiMangcSFMvAd8NBwH8AfmRb6iBbHxLgx3J59P",
                    "edpkumCFhgS94cjZXiFnnq7MFsaWBz4Tp78AX2fZfhB9J9hcgcKxgy"
                ],
                "group_threshold": "2"
            },
            ...
        ],
        "overall_threshold": "4"
    },
    "pour_info": {
        "pour_dest": "tz3bTdwZinP8U1JmSweNzVKhmwafqWmFWRfk",
        "pour_authorizer": "edpkteDwHwoNPB18tKToFKeSCykvr1ExnoMV5nawTJy9Y9nLTfQ541"
    },
    "replay_counter": "6505"
}

and you need just the first signatory from the second key group, you can do .../storage?path=key_info.key_groups.1.signatories.0, so you will receive just

edpkukogJzCZSAfc5foRpEZGsryMjiXj77VxcFLzZoreB1vZWFeKc2