SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3447f0d1ac476ba4228d88897d6a0af43ad15972d46d9520b31643df86f26be8' 
  AND token = 'ndZuz8Qr7qPJe+QkA7wPmdKXKO6GKErALscFWZqvJfg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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