Log compaction behavior with or without bootstrap is not consistent

[vordimous]

Describe the bug

The below data shows how many versions of a keyed object get returned from the same topic. If no_updates were coming into the topic then the cache was correct and showed only the latest message. if the topic was updating with multiple new versions of the same keyed object being submitted within a few seconds the result would include multiples of the same keyed object.

Individual fetch requests with object keys and the count of objects returned for each key:

fetch_no_updates_1", {
  air_quality: 1,
  freezer: 1,
  lamp/1: 1,
  lamp/2: 1,
  temperature/basement: 1,
  temperature/roof: 1
}
"fetch_updating_1", {
  air_quality: 4,
  freezer: 5,
  lamp/1: 6,
  lamp/2: 6,
  temperature/basement: 4,
  temperature/roof: 4
}
"fetch_updating_2", {
  air_quality: 2,
  freezer: 2,
  lamp/1: 3,
  lamp/2: 4,
  temperature/basement: 2,
  temperature/roof: 2
}
"fetch_updating_3", {
  air_quality: 3,
  freezer: 2,
  lamp/1: 3,
  lamp/2: 3,
  temperature/basement: 2,
  temperature/roof: 2
}
"fetch_no_updates_2", {
  air_quality: 1,
  freezer: 1,
  lamp/1: 1,
  lamp/2: 1,
  temperature/basement: 1,
  temperature/roof: 1
}

To Reproduce

• Actively send updates to multiple keyed objects on a log-compacted topic.
• fetch the full list of messages from that topic over HTTP

Expected behavior
a consistent return of only one message per key when a topic is log-compacted or an indication of when the race condition is possible.