SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = '251f1600a750ec0964f6f06d82d6cfff64a49f9738ca8162f17b3ebdd7d6440c' 
  AND token = 'U0x3sbjj3KQ05MuttQcfGPGZq7zYlevWGbmP+SmmjhY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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