Stopping Concurrent Double Bookings - PostgreSQL EXCLUDE Constraints
Overlapping bookings for one room arrive together. A PostgreSQL EXCLUDE constraint accepts only one. How to declare it, and how it works.
concurrency
4 posts
Running a Notification System with BullMQ, Part 5 - The Queue Guarantees No Order: Concurrency in Group Sends
Grouping 10,000+ notifications makes chunk jobs finish out of order. waiting-children keeps one group and one send; invariants check the five races closed.
Relearning Java Concurrency Control from the Ground Up
How the JVM monitor behind synchronized works, what ReentrantLock adds, and a producer-consumer fix. Then lock striping on per-user keys to raise throughput.
Solving a Concurrency Problem with a Single UPDATE
1,000 people request 100 items at once. How a single UPDATE gives one to exactly 100 of them, instead of the locks usually proposed for a first-come event.