react-plotly.js and Plotly.js: State Synchronization and Render Performance

Direct answer

The integration avoids full component re‑renders by keeping the Plotly DOM node stable and only triggering a Plotly update when the data or layout reference actually changes. For large or frequently mutated datasets the recommended pattern is:

1. Memoize the data and layout objects with useMemo so a new reference is created only when the underlying values change.
2. If you must mutate an array or object in place, increment the revision prop (or change the component key) to force a Plotly.react diff.
3. For small, frequent updates (e.g., appending a few points) use the imperative Plotly.update via the component ref or the usePlotly.js hook – this updates the trace without recreating the figure.
4. When the dataset is large (> 100 k points) switch to WebGL‑backed trace types (scattergl, heatmapgl, etc.) to reduce SVG node count and improve interaction performance.

Confirmed facts

• react-plotly.js synchronizes React data and layout props to the underlying Plotly instance, typically calling Plotly.react on prop changes to diff and update the existing DOM node.
• The wrapper relies on shallow prop comparison; a new object reference is required for React to detect a change.
• The revision prop (or a changed key) forces the wrapper to treat the props as changed, triggering a Plotly.react call even if the reference is unchanged.
• Imperative updates are possible through the ref API or the usePlotly.js hook, which calls Plotly.update to modify specific traces without a full figure replacement.
• SVG‑based traces scale poorly with point count; WebGL traces reduce DOM overhead and improve pan/zoom responsiveness for large data.

Likely explanation

If you see stutter or flicker when updating large datasets, it is often caused by creating new array or object references on every render (e.g., inline [{x:…, y:…}]) which triggers a Plotly.react call each time. Conversely, mutating the data in place without changing the reference prevents React from detecting the change, so the plot appears stale unless you manually bump revision or use an imperative update.

Recommended steps

1. Wrap your data and layout creation in useMemo, supplying dependencies that truly change the underlying values.
2. When you need to mutate an array (e.g., push a new point), create a new array ([...data, newPoint]) or use immutable update patterns, then let the memoized reference change.
3. If you prefer to keep the same reference for performance reasons, increment a numeric revision state variable and pass it as a prop; this signals the wrapper to call Plotly.react.
4. For rapid, small‑scale updates, obtain the Plotly instance via ref (or usePlotly.js) and call Plotly.update(gd, updateObj) with only the changed trace properties.
5. Profile with React DevTools Profiler to confirm that the Plotly component does not re‑render on every tick, and verify that Plotly.update is being used when appropriate.

Diagnostic detail needed

Are you currently using SVG‑based traces (e.g., scatter) or WebGL‑backed traces (scattergl, heatmapgl, etc.)? Knowing this will determine whether switching trace types is a necessary performance improvement.