Queues, Streams, and Event-Driven Design

Design asynchronous workflows that survive retries, partial outages, and high fanout.

35 min

3 sections

queues

events

kafka

01. Use async boundaries for resilience

Section 1 of 3

Queues decouple user-facing latency from slow work like email, indexing, fraud scoring, image processing, billing exports, and partner webhooks. The tradeoff is eventual consistency and more operational complexity.

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Order placement flow:

API receives order
  -> transaction writes order + outbox event
  -> response returns order_id

Outbox relay publishes OrderPlaced
  -> payment worker authorizes payment
  -> inventory worker decrements stock
  -> email worker sends confirmation
  -> analytics worker updates metrics

Caching Strategies

Database Selection and Consistency

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