Web Worker vs main thread for heavy browser compute

Learning goals

• Will this work steal time from input, paint, or scrolling?
• Is the job mostly data processing or mostly DOM-coupled work?
• What does it cost to move data across the thread…
• How will you handle cancellation, partial progress, and stale results?

Key decisions to discuss

• Pick a direction for this exact prompt, not the universal winner.
• State the trade-off that matters most for this scenario.
• Name when another option becomes the better answer.
• Keep the explanation grounded in concrete constraints.

Evaluation rubric

• Strong answers tie the recommendation to the prompt.
• Good tradeoff reasoning explains downsides, not just upsides.
• The answer should show when the recommendation stops being right.
• Follow-up pressure should not break the argument.

Constraints / Requirements

• Which direction would you defend for this prompt, and how would you explain when the other option is…
• Fits best when the computation is light, tightly coupled to DOM work, or too small to…
• Fits best when CPU-heavy browser work would otherwise compete with input, scrolling, and paint on the…

Options on the table

Keep the work on the main thread: Fits best when the computation is light, tightly coupled to DOM work, or too…
Move heavy compute into a Web Worker: Fits best when CPU-heavy browser work would otherwise compete with input, scrolling, and paint…

Common pitfalls

• Arguing from preference instead of prompt constraints.
• Pretending one option is always the winner.
• Ignoring the main downside of the chosen direction.
• Failing to explain when the alternative becomes stronger.

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