SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9a68c589b543b701d8aeafe5b346288c8f2636b3b74d45adee0641b1211fd6d6' 
  AND token = 'BowxLa5dv0XJDZJhio/fY+UxEI/BkF8dCYaYjMjtiNg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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