SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '76957f4767569ca92ce14dccc99b26d7f6f8dbe63be8073d451a8aac80c8c961' 
  AND token = 'EzosNOw3wtnNbWVHOY97QLxY6JQmmS8da1iyKUAGOYQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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