SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1669c864f4610d6657714705903720ee931017b9b6e9053536a0326b8ca83793' 
  AND token = '+BU4Q875KFxbtSIwtoBPAhtYDEbcvIgJCJSd2zVOlz8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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