SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '4f51abdd0ffd71de23069c9fb9864702af73823b8ea76a729771f549bcf834ca' 
  AND token = 'WCoukcita6t2JSJmrH0zIznVNBlMh0lcSRA6Qf7YDAc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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