SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '58997cf9773e14818070330d9b87015ae23adee6c17f5934ca7c51da93da967c' 
  AND token = 'RpH+ss1JZmu6nAWFhMmYy/nrL+fd6BQ69jB58QLHpuo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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