SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '712f641dfc30d9791a7bbd7a9ad5bd4f60b15422579da07747465964e3788263' 
  AND token = '6izE/9psQj1h5KveFjdJpio7YZbAmCJX9pyqyDMTfHY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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