Unclean Leader Election
When no safe leader candidate remains, unclean election can restore availability from a lagging replica while losing acknowledged records. Check ISR and eligible leader replicas.
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Log Compaction
Time-based retention forgets by age; compaction forgets by key. One keeps a recent window of events, the other keeps the latest value for everything.
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Topic Partition
Order exists inside a partition and nowhere else. Choosing the key decides what stays ordered; choosing the count decides how many consumers can work.
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Kafka Log, Replication, and Consumption
Order lives inside a partition, durability comes from in-sync replicas, and consumers hold their own place in the log. The rest is still your problem.
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Kafka Fundamentals
Understand Kafka ordering, delivery guarantees, replay, commit boundaries, retention gaps, and hot partitions.