𝗞𝗮𝗳𝗸𝗮 + 𝗜𝗱𝗲𝗺𝗽𝗼𝘁𝗲𝗻𝗰𝘆
Most distributed systems don’t fail loudly.They fail silently with duplicate processing.
I learned this the hard way.
In event-driven systems, retries are inevitable:
• Consumer crashes
• Network glitches
• Reprocessing
👉 Result: Same event processed multiple times
The fix is not “prevent retries”
The fix is design for idempotency
Simple rules:
• Use unique event IDs
• Maintain processed state
• Make operations repeat-safe
If your system breaks on duplicate events,
it’s not fault-tolerant yet.
𝗥𝗲𝗮𝗹 𝘀𝗰𝗮𝗹𝗮𝗯𝗶𝗹𝗶𝘁𝘆 𝘀𝘁𝗮𝗿𝘁𝘀 𝘄𝗵𝗲𝗻 𝗱𝘂𝗽𝗹𝗶𝗰𝗮𝘁𝗲𝘀 𝘀𝘁𝗼𝗽 𝗵𝘂𝗿𝘁𝗶𝗻𝗴 𝘆𝗼𝘂.
Even if producer retries sending same message multiple times, system handle duplicates by using the simple rules stated, aka 𝗗𝗲𝘀𝗶𝗴𝗻 𝗳𝗼𝗿 𝗜𝗱𝗲𝗺𝗽𝗼𝘁𝗲𝗻𝗰𝘆