---
title: Runtime constraints
description: Constraints of the Kibana runtime environment that plugin authors should understand and respect.
url: https://docs-v3-preview.elastic.dev/elastic/kibana/tree/main/extend/contributing/codebase/runtime-constraints
products:
  - Kibana
---

# Runtime constraints
Avoid these common mistakes when writing plugin code.

## Treating Kibana's filesystem as durable storage

Plugins should rarely, if ever, access Kibana's filesystem directly. Kibana instances are commonly ephemeral and anything written to the filesystem will potentially not be there on restart.

## Storing state in server memory

There are generally multiple instances of Kibana all hosted behind a round-robin load-balancer. As a result, storing state in server memory is risky as there is no guarantee that a single end-user's HTTP requests will be served by the same Kibana instance.

## Using WebSockets

Kibana has a number of platform services that don't work with WebSockets, for example authentication and authorization. If your use-case would benefit substantially from websockets, talk to the Kibana Core team about adding support. Do not hack around this limitation.