{
  "database_then_delete_old_refill": {
    "cache": {
      "expires_at": null,
      "value": "old",
      "version": 1
    },
    "database": {
      "expires_at": null,
      "value": "new",
      "version": 2
    },
    "stale": true,
    "trace": [
      "R miss then read DB version=1",
      "W commit DB version=2",
      "W delete empty cache",
      "R unconditional set version=1 after delete"
    ]
  },
  "delayed_double_delete": {
    "refill_after_second_delete": {
      "cache": {
        "expires_at": null,
        "value": "old",
        "version": 1
      },
      "refill_at": 4,
      "second_delete_at": 3,
      "stale": true
    },
    "refill_before_second_delete": {
      "cache": null,
      "refill_at": 2,
      "second_delete_at": 3,
      "stale": false
    }
  },
  "invalidate_then_old_refill": {
    "cache": {
      "expires_at": null,
      "value": "old",
      "version": 1
    },
    "database": {
      "expires_at": null,
      "value": "new",
      "version": 2
    },
    "stale": true,
    "trace": [
      "W delete cache; generation=1",
      "R miss then read DB version=1",
      "W commit DB version=2",
      "R unconditional set version=1"
    ]
  },
  "lease_fence": {
    "cache": {
      "expires_at": null,
      "value": "new",
      "version": 2
    },
    "fresh_fill_accepted": true,
    "generation_after_invalidation": 1,
    "old_token": 0,
    "stale_fill_accepted": false
  },
  "model": "deterministic cache-aside race model",
  "not_modeled": [
    "a real memcached server or database",
    "network transport, process crash, or arbitrary schedules",
    "clock accuracy, eviction policy, or production performance"
  ],
  "per_key_serialization": {
    "cache": {
      "expires_at": null,
      "value": "new",
      "version": 2
    },
    "stale": false,
    "trace": [
      "W acquire key lock",
      "W commit DB version=2",
      "W delete cache",
      "W release key lock",
      "R acquire key lock and observe miss",
      "R read DB version=2 and fill cache"
    ]
  },
  "ttl": {
    "meaning": "TTL bounds this modeled stale interval; it does not prevent stale reads before expiry",
    "read_at_10": null,
    "read_at_9": {
      "expires_at": 10,
      "value": "old",
      "version": 1
    }
  },
  "version_fence": {
    "cache": {
      "expires_at": null,
      "value": "new",
      "version": 2
    },
    "fresh_fill_accepted": true,
    "minimum_version": 2,
    "stale_fill_accepted": false
  }
}