Will Virtual Threads Change the Way We Handle Multi-threading?

The main advantage of virtual threads is that they let you write blocking code while maintaining efficiency. However, if you're already familiar with CompletableFuture, switching to virtual threads may not give you significant performance gains unless you're dealing with a massive number of concurrent IO operations. It's best to assess your specific use cases.

You're correct in thinking that using virtual threads can allow for parallel execution. The main goal of virtual threads is not just parallelism but also writing simpler, non-blocking code. Just make sure you have enough connections available in your pool to handle those requests simultaneously, otherwise you might hit a bottleneck if too many threads are trying to access the same resource at once.

You’re on the right path! Just be informed that if you're making a lot of blocking calls, that could limit the effectiveness of virtual threads, as too many could tie up your available platform threads. If you're planning a lot of reads from Redis, consider their threading model too, since older versions have limitations.

For combining slow calls, using CompletableFuture or virtual threads both can work. With CompletableFuture, just ensure you don't block it too early; start all your futures before you join them. If you properly handle async calls, you can achieve the parallel execution you're looking for.

Yes, you're right about the total time being 3 seconds if you manage your requests properly with CompletableFuture. Just be cautious about your system's constraints. If your connection pool is limited, too many simultaneous requests can lead to slowdowns.