Apache Kafka Fundamentals Study Guide — CCDAK

Apache Kafka Fundamentals – CCDAK Study Guide

This is the largest domain (40% of the exam) and covers Kafka's core architecture and the developer-facing behavior of topics, partitions, producers, and consumers. Nearly half your marks live here, so master partitions, replication, delivery semantics, and the producer/consumer knobs cold. The CCDAK is developer-focused, so questions emphasize how you configure and reason about Kafka, not cluster operations.

Topics, Partitions, and Brokers

• A topic is a named logical event stream, split into partitions distributed across brokers.
• The partition is the unit of:
  • Parallelism — within a consumer group, each partition is read by exactly one consumer.
  • Ordering — Kafka guarantees order only within a partition (by offset).
  • Storage — each partition is an append-only log.

Keys and partitioning: the default partitioner hashes the record key, so same-key records land in the same partition — the mechanism to preserve ordering for related messages. No key → round-robin/sticky distribution.

Replication and Durability

• Replication factor — number of copies of each partition across brokers (e.g., RF=3 tolerates up to 2 broker losses, subject to ISR).
• Leader and followers — one replica is the leader (handles reads/writes); followers replicate.
• In-sync replicas (ISR) — replicas caught up with the leader. acks=all waits for the ISR.
• min.insync.replicas — minimum in-sync replicas required to accept a write; with acks=all, if fewer are in sync, the produce fails (protecting durability).