You need to implement a feature that processes heavy image files asynchronously. How would you set up and manage these operations in Spring Boot?

Heavy, time-consuming work like image processing should run asynchronously in Spring Boot, using @Async on a dedicated service method so the request thread isn't blocked waiting for it to finish.

Key Points: • @EnableAsync on a configuration class turns on Spring's asynchronous method execution support. • @Async on the processing method makes Spring run it on a separate thread from a configured executor, returning immediately to the caller. • A custom ThreadPoolTaskExecutor bean should be configured explicitly, since the default executor isn't tuned for CPU/IO-heavy workloads like image processing. • Returning a CompletableFuture<T> from the @Async method lets the caller track completion or chain further processing once the result is ready. • Monitoring queue size and thread pool utilization prevents the executor from silently backing up under sustained heavy load.

Example: A photo-upload endpoint saves the file and immediately returns a 202 Accepted response to the user, while a separate @Async method resizes and processes the image in the background and updates the record once finished.

Code Example:

@Configuration
@EnableAsync
public class AsyncConfig {

    @Bean(name = "imageExecutor")
    public Executor imageExecutor() {
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        executor.setCorePoolSize(4);
        executor.setMaxPoolSize(8);
        executor.setQueueCapacity(100);
        executor.initialize();
        return executor;
    }
}

@Async("imageExecutor")
public CompletableFuture<String> processImage(byte[] imageData) {
    // heavy processing
    return CompletableFuture.completedFuture("done");
}

Interview Tip: A concise interview answer is:

"I'd enable @EnableAsync and mark the processing method @Async, backed by a dedicated ThreadPoolTaskExecutor sized for this kind of CPU-heavy work rather than the default executor. The endpoint returns immediately, and the method returns a CompletableFuture so callers can track completion without blocking the request thread."