SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '31a18486a4c172a88fd8afdaff41cd60e888dea31f1c30adb51626c412470f42' 
  AND token = 'mrBKba762Z/9irYdriCMteJjUK7rSEHik8ioSIlbXt8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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