Event Ledger

Read the evidence

1. Correctness first. Every measured replay checks its final order-state digest against the reference. JUnit separately checks semantics, state invariants, random streams and concurrent delivery.
2. Service is not end-to-end latency. Scheduled-to-done includes producer scheduling lag, backpressure, queue wait and processing. Arrival deadlines never reset to hide backlog.
3. All rounds remain visible. Tables show medians of per-round percentiles, their observed ranges and the worst individual sample. They are not pooled percentiles.
4. Allocation boundaries matter. Consumer bytes exclude event generation, book initialization, producer envelopes and retained memory. A zero does not mean the whole application allocates nothing.

Tradeoffs and limits

The array book requires dense IDs and a bounded tick range, trading fixed memory for lower per-event allocation. The reference implementation accepts the same bounds for a comparable experiment. Neither is a matching engine. The queue is a standard bounded ArrayBlockingQueue, not a custom lock-free structure.

Desktop scheduling, clock instrumentation and a volatile result sink affect the results. No pinned cores, Linux hardware counters, exchange feed, kernel bypass or wire-to-wire timestamps are included. Repeat on controlled hardware; do not put these figures on a resume without the workload and measurement boundary.

Environment and source provenance

{
  "workload": "synthetic seed=42; 4096 dense IDs; 8192 ticks; 300000 service / 60000 queued events",
  "flags": "-Xms512m -Xmx512m -XX:+UseG1GC",
  "os": "Microsoft Windows NT 10.0.26200.0",
  "cpu": {
    "Name": "13th Gen Intel(R) Core(TM) i9-13900HK",
    "NumberOfCores": 14,
    "NumberOfLogicalProcessors": 20
  },
  "recordedAt": "2026-10-04T22:05:32.1140206Z",
  "source": [
    {
      "path": "src\\main\\java\\io\\github\\bigfiiish\\eventledger\\ArrayBook.java",
      "sha256": "03C0EA027C8EA8277E330F7AC3EBD6B7F4D6E764075FB76C7FCE7E1B22FB8ADF"
    },
    {
      "path": "src\\main\\java\\io\\github\\bigfiiish\\eventledger\\Benchmark.java",
      "sha256": "36ECAC36D95FD2F2E79AAA23ABDD8E683ED25E3B70CFC6F836255889127DB3C6"
    },
    {
      "path": "src\\main\\java\\io\\github\\bigfiiish\\eventledger\\Book.java",
      "sha256": "DB3A490EABD13869DA8C1222129387B7D219C8AAF9ED01D0525186F2C355C5E9"
    },
    {
      "path": "src\\main\\java\\io\\github\\bigfiiish\\eventledger\\Event.java",
      "sha256": "B012209E72DB8B8C374E4F9244D25AEE1BAE81A29A9BC872718BDBCF7819D890"
    },
    {
      "path": "src\\main\\java\\io\\github\\bigfiiish\\eventledger\\Journal.java",
      "sha256": "6759984696F1F772D8D6699EF73D189F6C2151412CAF35D1CEF3349C83D46D8C"
    },
    {
      "path": "src\\main\\java\\io\\github\\bigfiiish\\eventledger\\ReferenceBook.java",
      "sha256": "A22D92B1CB6597F005F3DF836241806A07012E666FCD477A6A8547506C42FD67"
    },
    {
      "path": "src\\main\\java\\io\\github\\bigfiiish\\eventledger\\Replay.java",
      "sha256": "229808C963D2BC0B7080F09D15F75F4D4ED471A31043C76D480458114E6B7904"
    },
    {
      "path": "src\\main\\java\\io\\github\\bigfiiish\\eventledger\\Workload.java",
      "sha256": "D297D55BBF0966D5F3464009DA227487CBAB3746EE89277B259EA2815A133F70"
    },
    {
      "path": "src\\test\\java\\io\\github\\bigfiiish\\eventledger\\BookTest.java",
      "sha256": "EB765D60B9145C1723EDEB50E4B9F7EFAC1B91166C5AAA48E06FFDAC16D2FFDA"
    }
  ],
  "java": "openjdk version \"21.0.12\" 2026-07-21 LTS\r\nOpenJDK Runtime Environment Microsoft-14653896 (build 21.0.12+8-LTS)\r\nOpenJDK 64-Bit Server VM Microsoft-14653896 (build 21.0.12+8-LTS, mixed mode, sharing)\r\n"
}

Download all measurements and provenance JSON