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  "path": "/abs/2606.19210v1",
  "publishedAt": "2026-06-18T00:00:00.000Z",
  "site": "https://arxiv.org",
  "tags": [
    "Faruk Alpay",
    "Levent Sarioglu"
  ],
  "textContent": "**Authors:** Faruk Alpay, Levent Sarioglu\n\nApproximate membership queries in streams often need recent-window semantics rather than membership over all items ever seen. This paper studies guarded epoch Bloom filters, a sliding-window alternative to counting and stable Bloom filters. The structure partitions a fixed bit budget into rotating epochs, inserts only into the current epoch, clears whole segments at epoch boundaries, and keeps one additional guard epoch. This guard yields a deterministic live-window invariant: every item inserted in the last W positions remains represented, while rotation-induced stale retention is bounded by one epoch beyond the target window. We give the construction, prove its live-coverage and bounded-staleness properties, derive a false-positive approximation, and include a blocked variant that improves locality by confining probes to one block per epoch. Experiments cover 225 synthetic streaming configurations and 45 configurations from a timestamp-ordered web-server access-log stream. At 14 bits per live item, the guarded epoch filter reduces median synthetic false positives from 0.191 for a four-bit counting Bloom baseline to 0.02225 while preserving zero measured live-key false negatives. The method is not a replacement for exact deletion; it targets systems where bounded stale positives are acceptable but false negatives inside the live window are not.",
  "title": "Guarded Epoch Bloom Filters for Sliding-Window Membership"
}