DepositPerItem

Constant v334 → current u64

Charges for storage structure, not just bytes.

Current Value

0.000000075 TAO (75 raw)

Conversion: ÷ 10^9 (RAO → TAO)

Relevant for: developers

The Big Picture

Beyond bytes, each storage key costs a flat deposit. This discourages creating many small items. Total storage deposit = (items * DepositPerItem) + (bytes * DepositPerByte).

From Chain Metadata

The amount of balance a caller has to pay for each storage item. # Note Changing this value for an existing chain might need a storage migration.

Use Cases

  • Estimate storage costs for contract state
  • Optimize storage item count

Code Examples

import { createClient, Binary } from "polkadot-api";
import { getWsProvider } from "polkadot-api/ws";
import { sub } from "@polkadot-api/descriptors"; // generated by: npx papi add sub -w wss://entrypoint-finney.opentensor.ai:443

const client = createClient(getWsProvider("wss://entrypoint-finney.opentensor.ai:443"));
const api = client.getTypedApi(sub);

// Query DepositPerItem constant
const value = await api.constants.Contracts.DepositPerItem();
console.log("DepositPerItem:", value);
// Balance: divide by 10^9 for TAO
const tao = value / 1_000_000_000n;

Type Information

Type
u64
Byte Size
8 bytes
Encoding
fixed
Raw Hex
0x4b00000000000000

Runtime Info

Pallet
Contracts
First Version
v334
Latest Version
v334
Current Runtime
v411