Diagnosing Slow Author Experience After a Component Rollout
After a release that added 6 new components and a large client library, authors on a 12-site AEM instance report the page editor takes 25–40 seconds to load and sometimes hangs. The release also enabled a new personalization tag on every page. Symptoms: the editor is slow but published pages are fast; the issue is worst on sites with the most components on a page; a few authors on older browsers see it most. The team has no APM on author, only publish. There are 200 components total, and the new client library is 3.5 MB unminified. The release is live and the business wants a fix within 48 hours.
1. Given no APM on author, how do you localize the cause quickly and what are the most likely culprits?
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Localize with browser tooling and targeted tests, since APM is absent.
- Browser network waterfall on a slow page: identify whether time is spent in a few large requests (client library, component JS/CSS) or many small ones (component dialogs loading).
- Compare pages: a page with few components vs many. If load time scales with component count, the editor is loading per-component resources or initializing heavy dialogs.
- Disable the new client library via a test config and re-measure; then disable the personalization tag; isolate variables one at a time.
- Check author Dispatcher/cache if present, and whether the new components trigger server-side calls on editor load.
Most likely culprits, ranked:
- 3.5 MB unminified client library loaded on author: huge parse/execute cost, worst on older browsers. Unminified is a red flag-minify and split.
- Per-component resource loading: 6 new components each pulling JS/CSS on editor load, scaling with component count (matches the symptom).
- Personalization tag on every page adding a blocking third-party call in the editor.
- Heavy dialog initialization in the new components.
The 'published fast, author slow' split points at author-only assets (editor clientlibs, dialogs, personalization) rather than content delivery.
2. What immediate mitigation do you ship within 48 hours, and what is the permanent fix?
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48-hour mitigation (low risk, reversible):
- Minify and split the client library; load only what the editor needs on author via a dedicated author clientlib category. This alone often cuts multi-second parse time.
- Defer or remove the personalization tag from author (it has no authoring value).
- Lazy-load the 6 new component dialogs so they initialize only when opened.
- Feature-flag the changes so a bad mitigation can be reverted in minutes.
Permanent fix:
- Author clientlib strategy: separate author vs publish clientlibs; enforce size budgets in CI (e.g., fail if author clientlib exceeds a threshold).
- Component performance standard: dialogs must lazy-init; no synchronous third-party calls in the editor.
- Instrument author: add APM/RUM to the author tier so the next regression is visible immediately, not after author complaints.
- Browser support policy: decide explicitly whether older browsers are supported; if not, communicate and stop chasing them.
Sequencing: mitigation first to stop the bleeding, then instrumentation so you can prove the permanent fix worked.
3. How do you prevent this class of regression from recurring across 12 sites and 200 components?
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- Performance budget in CI: thresholds on author clientlib size and component count per page; block merges that exceed them.
- Release checklist includes an author-experience smoke test on a representative heavy page, not just publish checks.
- Component review gate: new components must declare their author-side assets and lazy-init behavior; reviewers check it.
- Author RUM/APM as standing telemetry with alerts on regression.
- Canary rollout: release to one site first, measure, then expand-rather than all 12 at once.
- Post-incident review with a documented root cause and a follow-up item to close the instrumentation gap that made this hard to diagnose.