SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '73be888afc2f4b12d7e25bcb4c0988fd385b5ee54204732f3c5d666973f3f9a8' 
  AND token = 'ekXMWj2BuFMJMLNHE3lRxeqQ3iKEQ2o42iAX+DvDYEw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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