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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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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Log Sequence Number (LSN)
A log sequence number points at a place in the transaction log. It is how a pipeline knows the order of changes, where to resume, and what to ignore.
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Incremental Snapshot
Seeding a table no longer has to mean one long locked scan. Chunks and watermarks let a snapshot run beside the change stream, and pause and resume.
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Incremental Loading and CDC
A nightly job filtering on updated_at looks right until rows quietly go missing. Here is how each change-capture method works, and what none of them can see.
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Raft
Raft gets several servers to agree on a shared state and keeps working while a majority survives — designed above all to be understandable.
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Replication, Consistency, and Time
Once data has two copies, they can disagree. See what each replication scheme costs, what the models between strong and eventual promise, and when clocks lie.
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Merkle Tree
A hierarchy of hashes lets two replicas locate exactly which ranges differ — without sending or comparing every row they hold.
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Quorum
A quorum sets how many replicas must respond. Overlap gives read and write sets a shared replica, while retention and version-selection rules determine what a read returns.
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Eventual Consistency
Replicas converge on a record once updates to it stop — with no bound on how long, and no statement about what a reader sees meanwhile. Both gaps matter.