SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '0294e98742ab652154cb2695d7376a6a16b847625bdece13db8a4e09541d1fcc' 
  AND token = 'n0lMEv5l70B1WfEKHUDIuuCmTYZwLGy9LbNJapE+PLs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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