SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6c4b5787908ed07dcab27d2cd2fa76368d84bbff07f4dab144c29b97377e3617' 
  AND token = 'LxR1hDBZD00sEY+I5lqksjlNMWL+j/zbOhAQOnHdN3U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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