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Mongo aggregation filter optimization

Skill kjuhwa/skills-hub/skills/backend/mongo-aggregation-filter-optimization

Replace `$unwind`+`$match` on array sub-documents with inline `$filter` so array elements are pruned before any downstream stage — avoids N× document explosion.From its SKILL.md

Install
npx -y skills add kjuhwa/skills-hub --skill mongo-aggregation-filter-optimization

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SKILL.md

0.6 KB, 6 tokens by cl100k_base, as published. Nobody here has run it

See content.md.

What ships with it: 1 file

1.6 KB alongside SKILL.md

Gives 0 of the 12 instructions most performance cost skills give in 6 tokens

Counted across 803 of the 1,058 authors here whose files we hold, read 2026-08-07

  • Keep skill files under 500 lines or tokensin 82 of 803, across 16 files
  • Use imperative form in instructionsin 80 of 803, across 9 files
  • Draft assertions while test runs are in progressin 75 of 803, across 9 files
  • Create two to three realistic test promptsin 74 of 803, across 9 files
  • Write skill descriptions to be pushyin 72 of 803, across 7 files
  • Save test cases to evals JSONin 72 of 803, across 6 files
  • Ask questions about edge cases and input formatsin 72 of 803, across 7 files
  • Save timing data immediately when runs completein 70 of 803, across 5 files
  • Include all trigger conditions in the skill descriptionin 69 of 803, across 3 files
  • Launch all test runs in a single turn or simultaneouslyin 69 of 803, across 3 files
  • Capture intent before writing a skillin 67 of 803, across 1 file
  • Import directly instead of barrel filesin 52 of 803, across 15 files

Said here and by no other author read

  • replace $unwind and $match with $filter
  • prune array elements before downstream stages

Grouped from the skills themselves: near-identical wordings counted once, and counted by distinct author, so one author publishing three of these counts once. Length counted with cl100k_base; the agent that loads this file may tokenize it differently.

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