Performance impact of the SDKs

A monitoring tool should not slow down the app it watches. This page says what the SDKs cost and how to keep that cost low.

Size

Package	Minified	Gzipped
`@watchdog-sdk/browser`	about 16 KB	about 6 KB
`@watchdog-sdk/react-native`	about 15 KB	about 6 KB

Session replay is an optional extra (@rrweb/record) loaded only when you turn replay on, so it is not in the numbers above.

At start-up: the SDK reads the DSN, sets up a few listeners and wraps fetch, XMLHttpRequest, console and history. Nothing is sent and no timers run until something happens.
When an error happens: it builds one event and sends it in the background. Repeats of the same error are dropped for a short time, and there is a per-minute cap, so an error loop cannot flood the network.
Breadcrumbs: at most 100 are kept in memory. Console arguments are summarized to a short, bounded text, so logging a huge object costs microseconds, not milliseconds.
Sending: one request at a time, with a small queue (the oldest event is dropped when it fills) and backoff when the server is slow or down. Sending never blocks your code.
Metrics: batched and sent every few seconds. The timer does not keep a Node.js process alive.

Setting	What it does
`sampleRate`	Share of errors to send (0 to 1).
`tracesSampleRate`	Share of transactions to send. On a busy server, use a low value such as `0.1`.
`maxTransactionsPerMinute`	Hard cap on transactions sent per minute. Default 300.
`maxEventsPerMinute`	Hard cap on errors sent per minute.
`replay.sampleRate`	Share of sessions recorded. Default 10%. Replay is the heaviest feature, so record only what you need.
`integrations`	Turn off breadcrumb sources you do not use, such as `console` or `network`.

Keep tracesSampleRate low on high-traffic servers. Most of the value comes from a sample.
Turn replay on for a small share of sessions, or only in production on pages where it helps.
If you do not need request breadcrumbs, set integrations: { network: false }.