Software Engineering

Spring Boot makes it easy to schedule recurring tasks using the @Scheduled annotation. This works well for a single application instance, but what happens when the application is deployed across multiple servers or regions? Each instance runs its own scheduler, meaning the same task may execute concurrently on several instances. For some workloads, this is harmless. For others, such as importing data, publishing notifications, or performing periodic cleanup, concurrent execution can cause duplicate processing or conflicting updates. ...

How do you safely retry a POST request when the outcome is unknown? A comparison of stateless preconditions and idempotency keys, using funds transfers as an example.

Originally published in April 2022. Updated October 2026. Finding the best route between two points sounds simple until the map contains hundreds of intersections, roads with different travel costs, and areas that should be avoided altogether. This is the shortest-path problem: given a graph and a cost for traversing each edge, find a path whose total cost is minimal. In this article, we’ll use a small graph to explore two classic shortest-path algorithms: Dijkstra’s algorithm and A search*. We’ll start with the fundamentals of graph theory and briefly explore breadth-first search (BFS), depth-first search (DFS), and Bellman–Ford before examining Dijkstra and A* step by step. ...