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2 stories

Banner: four event-driven architecture patterns shown as four connected service diagrams

Engineering Practice

Event-driven architecture patterns: notification, state transfer, event sourcing, CQRS

John Nguyen · Jul 12, 2026 · 8 min read

Event-driven is not one pattern but four, and teams get hurt when they mix them up. We compare event notification, event-carried state transfer, event sourcing and CQRS on one billing example, with the costs each one adds and the signals that tell you which fits.

Banner: a large monolith block gradually wrapped and replaced by smaller service blocks like a strangler fig vine

Engineering Practice

Monolith to microservices without a rewrite: our strangler fig migration plan

John Nguyen · May 15, 2025 · 8 min read

A proposal to split our Django monolith into 30 services landed on day one of planning. We said no, then spent 14 months extracting four services with a strangler fig: boundaries inside the monolith first, routing at the edge, shadow traffic, and data ownership moved last.