{
  "schemaVersion": 1,
  "generatedAt": "2026-07-22",
  "benchmark": "admin user created_at index representative cost gate",
  "environment": {
    "platform": "darwin",
    "arch": "arm64",
    "cpu": "Apple M4 Pro",
    "postgresImage": "postgres:18.2-alpine3.23",
    "container": "oxicloud-postgres-1",
    "client": "psql through docker exec"
  },
  "method": {
    "rowsPerDistribution": 500000,
    "independentTransactions": 3,
    "samplesPerTransactionAndShape": 5,
    "totalSamplesPerShape": 15,
    "warmupsPerTransactionAndShape": 1,
    "order": "A/B for the accepted timestamp-only result; a later A/B/C gate rotated no-index/simple/compound order inside every transaction",
    "harnessEvolution": "the current representative SQL is the expanded A/B/C version; the top-level distribution samples retain the earlier A/B authorization run, while compoundRepresentativeABC retains the later isolated rerun",
    "cleanup": "every transaction ended in ROLLBACK",
    "commonIndexes": "both baseline and candidate tables have the same UUID primary-key index",
    "insertBatchRows": 10000,
    "insertValues": "prebuilt identical A/B batches with new timestamps and an indexed sample selector"
  },
  "previousTiedFixtureComparison": {
    "timestampMultiplicity": 100,
    "indexBytes": 3448832,
    "uniqueToTiedIndexByteRatio": 3.263,
    "reasonForFollowup": "PostgreSQL posting-list deduplication compressed repeated created_at keys and understated a normal mostly-unique registration workload"
  },
  "uniqueTimestamps": {
    "distinctTimestamps": 500000,
    "indexBytesEachRound": [
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      11255808,
      11255808
    ],
    "indexBytesPerInitialUser": 22.512,
    "indexBytesAfter50000InsertsEachRound": [
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      13271040
    ],
    "firstPage": {
      "noIndexSamplesMs": [
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      ],
      "indexSamplesMs": [
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      "noIndexMedianMs": 57.217,
      "indexMedianMs": 0.215,
      "speedup": 266.13
    },
    "offset50000": {
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      "indexSamplesMs": [
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      "noIndexMedianMs": 126.377,
      "indexMedianMs": 5.219,
      "speedup": 24.21
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    "insert10000Rows": {
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      "noIndexMedianMs": 37.218,
      "indexMedianMs": 44.017,
      "extraMicrosecondsPerUser": 0.68
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    "correctness": {
      "initialOrderMatchesEachRound": [
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      ],
      "finalCountsMatchEachRound": [
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      ],
      "finalOrderMatchesEachRound": [
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      ]
    }
  },
  "tenUserBursts": {
    "distinctTimestamps": 50000,
    "indexBytesEachRound": [
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    ],
    "indexBytesPerInitialUser": 9.503,
    "indexBytesAfter50000InsertsEachRound": [
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    "firstPage": {
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      "indexSamplesMs": [
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      "noIndexMedianMs": 76.213,
      "indexMedianMs": 0.237,
      "speedup": 321.57
    },
    "offset50000": {
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      "indexSamplesMs": [
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      "noIndexMedianMs": 142.349,
      "indexMedianMs": 7.783,
      "speedup": 18.29
    },
    "insert10000Rows": {
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      "indexSamplesMs": [
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      "noIndexMedianMs": 34.996,
      "indexMedianMs": 40.819,
      "extraMicrosecondsPerUser": 0.582
    },
    "correctness": {
      "initialOrderMatchesEachRound": [
        true,
        true,
        true
      ],
      "finalCountsMatchEachRound": [
        true,
        true,
        true
      ],
      "finalOrderMatchesEachRound": [
        true,
        true,
        true
      ]
    }
  },
  "decision": {
    "status": "accepted_by_explicit_user_tradeoff",
    "productionVariant": "timestamp-only created_at DESC index accepted; compound index rejected and not present in production",
    "reason": "After seeing the corrected representative cost, the user explicitly accepted 11,255,808 bytes and +0.680 us per inserted user for unique timestamps (24.21x-266.13x read gains), plus 4,751,360 bytes and +0.582 us per user for ten-user bursts (18.29x-321.57x read gains). This decision does not cover the compound index. The isolated representative A/B/C follow-up rejected the compound index: it regressed the unique-timestamp first page and materially increased disk/write cost."
  },
  "compoundRepresentativeABC": {
    "status": "rejected",
    "candidate": "created_at DESC, id DESC compound index versus the accepted created_at DESC index",
    "method": {
      "rowsPerDistribution": 500000,
      "independentTransactions": 3,
      "samplesPerTransactionAndShape": 5,
      "totalSamplesPerShape": 15,
      "warmupsPerTransactionAndShape": 1,
      "order": "A/B/C order rotated inside every transaction",
      "cleanup": "every transaction ended in ROLLBACK",
      "commonIndexes": "all tables have the same UUID primary-key index",
      "insertBatchRows": 10000,
      "timingIsolation": "canonical rerun after other CPU/PostgreSQL benchmark agents stopped"
    },
    "indexStorage": {
      "uniqueTimestamps": {
        "simpleBytesEachRound": [
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          11255808,
          11255808
        ],
        "compoundBytesEachRound": [
          20275200,
          20275200,
          20275200
        ],
        "compoundMinusSimpleBytes": 9019392,
        "compoundToSimpleRatio": 1.8013,
        "compoundIncreasePercent": 80.131,
        "simpleBytesAfter50000InsertsEachRound": [
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          13271040,
          13271040
        ],
        "compoundBytesAfter50000InsertsEachRound": [
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        ],
        "afterInsertCompoundIncreasePercent": 80.247
      },
      "tenUserBursts": {
        "simpleBytesEachRound": [
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        ],
        "compoundBytesEachRound": [
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        ],
        "compoundMinusSimpleBytes": 15572992,
        "compoundToSimpleRatio": 4.2776,
        "compoundIncreasePercent": 327.759,
        "simpleBytesAfter50000InsertsEachRound": [
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        ],
        "compoundBytesAfter50000InsertsEachRound": [
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        ],
        "afterInsertCompoundIncreasePercent": 329.532
      }
    },
    "uniqueTimestamps": {
      "firstPage": {
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        "compoundSamplesMs": [
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        "noIndexMedianMs": 64.688,
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        "compoundMedianMs": 0.198,
        "compoundRegressionVsSimplePercent": 6.452
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        "noIndexMedianMs": 139.393,
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        "compoundSpeedupVsSimple": 1.627
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      "insert10000Rows": {
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        "simpleExtraMicrosecondsPerUserVsNoIndex": 1.3504,
        "compoundExtraMicrosecondsPerUserVsNoIndex": 1.0511,
        "compoundDeltaMicrosecondsPerUserVsSimple": -0.2993
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    },
    "tenUserBursts": {
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        "noIndexMedianMs": 82.563,
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        "noIndexMedianMs": 159.779,
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        "compoundSpeedupVsSimple": 2.304
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      "insert10000Rows": {
        "noIndexSamplesMs": [
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        "noIndexMedianMs": 40.612,
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        "simpleExtraMicrosecondsPerUserVsNoIndex": 0.3863,
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        "compoundDeltaMicrosecondsPerUserVsSimple": 0.4446
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    },
    "correctness": {
      "initialOrderMatchesEachRound": [
        true,
        true,
        true
      ],
      "finalCountsMatchEachRound": [
        true,
        true,
        true
      ],
      "finalOrderMatchesEachRound": [
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        true,
        true
      ]
    },
    "decision": "rejected: versus the accepted narrow index, the compound index regressed the common unique-timestamp first page by 6.45%, enlarged the btree by 80.13%-327.76%, and added 0.445 us/user to burst inserts. Its 1.63x-2.30x deep-page gains do not pass the no-regression resource gate."
  }
}