SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '31d85f00811686cded130bacf7994dbf6d082ea7c19b2b45b781ae0ed45adf94' 
  AND token = 'a7xrW3f+UXMZCBEiLJAZKkL34MQl03P675UCz5/4h2M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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