Flash Sale Inventory Engine Using Redis Lua

System Design diagram · made in Skemio

System design showing an API gateway routing checkouts to an order service using atomic Redis Lua scripts, pushing confirmed orders via Kafka into PostgreSQL.

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What it shows

Atomic Lua decrements: Read and reduce stock in a single Redis CPU tick.
Early rejection: 99% of out-of-stock traffic is rejected in under 1ms.
Asynchronous writes: Validated orders flow via queues to PostgreSQL.

The takeaway

Gate flash sale stock in Redis memory with atomic Lua scripts before touching relational databases.

#SystemDesign
#Redis
#PostgreSQL
#HighConcurrency
#SoftwareArchitecture
#BackendEngineering

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