The original architecture, optimized for concurrency, has been suffering from delays in notification delivery. Guardian readers can use the mobile app to access content and can register to receive breaking-news alerts via push notifications. The event-driven architecture (EDA) behind that has been operating since 2009 and over time notification delivery times have increased, taking more than five minutes for some users. The solution supporting push notification delivery utilizes a range of technologies. Based on these experiments, they increased the thread-pool size of Scala applications running in lambda functions to improve parallelism.

Source: The Guardian May 17, 2023 10:02 UTC