SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5135bf0e46eecac844ab8127d56579fd9eae138d9dfedab7c9a01e22c616c499' 
  AND token = 'RpcbcP8Rf2ucdSpVLl7mI8+lgWWh1bLCXu/nEXV7bOE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}