SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '250cb82ebcd4a621a10a3c62e208230684dcdb900dfb377f635e7f121090d16b' 
  AND token = 'N3pdaYalkUlXfoCERlYRnsTZeNCSqXDp4/aYhKrZV7Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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