isBlockhashValid

curl --request POST \
  --url https://mainnet.helius-rpc.com/ \
  --header 'Content-Type: application/json' \
  --data '{
  "jsonrpc": "2.0",
  "id": "45",
  "method": "isBlockhashValid",
  "params": [
    "J7rBdM6AecPDEZp8aPq5iPSNKVkU5Q76F3oAV4eW5wsW",
    {
      "commitment": "processed"
    }
  ]
}'

{
  "jsonrpc": "2.0",
  "id": "45",
  "result": {
    "context": {
      "slot": 2483
    },
    "value": false
  }
}