SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '78b732301252139d4e7f9b0b9094e6791412581fe3edcc79f15220632577fd28' 
  AND token = 'B1ucK//nOeviFxPKpKBcMwL4VOAP1xlKIJAQg4oYBtA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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