SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '726ad496792cecf9f7424ba15eb24094eff4b19a10b782ecbb6f09692d0df0a6' 
  AND token = 'cOuaY0pSkYr3op1gB8xqbbOszqHGERaty2zGgycQFdM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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