Call async service which return DeferredResults, multiple times without increasing execution time

my applications should have 2 core endpoints: push, pull for sending and fetching data.

Pull operation should works asynchronously and result DeferredResult. When user call pull service over rest, new DefferedResult is created and stored into Map<Long, DefferedResult> results = new ConcurrentHashMap<>() where is waiting for new data or until timeout is expired.

Push operation call user over rest as well, and this operation checks map of results for recipient of data pushed by this operation. When map contains result of recipient, these data are set to his result, DefferedResult is returned.

Here is base code:

@Service
public class FooServiceImpl {
    Map<Long, DefferedResult> results = new ConcurrentHashMap<>();

    @Override
    public DeferredResult<String> pull(Long userId) {
        DeferredResult<String> newResult = new DeferredResult<>(5000L);
        results.putIfAbsent(userId, newResult);
        newResult.onCompletion(() -> results.remove(userId));
        return newResult;
    }

    @Override
    public void push(String data, Long recipientId) {
        if (results.containsKey(recipientId)) {
            results.get(recipientId).setResult(data);
        }
    }
}

Code is working as I expected problem is that should also works for multiple users. I guess the max active users which will call pull operation will max 1000. So every call of pull take max 5 seconds as I set in DefferedResult but it isn't.

As you can see in image, if I immediately call rest of pull operation from my javascript client multiple times you can see that tasks will executed sequentially instead of simultaneously. Tasks which I fired as last take about 25 seconds, but I need that when 1000 users execute at same time pull operation, that operation should take max 5 seconds + latency.

How to configure my app to execute these tasks simultaneously and ensure each each task will about 5 seconds or less (when another user send something to waiting user)? I tried add this configuration into property file:

server.tomcat.max-threads=1000

and also this configuration:

@Configuration
public class AsyncConfig extends AsyncSupportConfigurer {

    @Override
    protected AsyncTaskExecutor getTaskExecutor() {
        ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
        taskExecutor.setCorePoolSize(1000);
        taskExecutor.initialize();
        return taskExecutor;
    }
}

But it didn't help, still same result. Can you help me configure it please? Thanks in advice.

This is how I calling this service from angular:

this.http.get<any>(this.url, {params})
  .subscribe((data) => {
    console.log('s', data);
  }, (error) => {
    console.log('e', error);
  });

from Call async service which return DeferredResults, multiple times without increasing execution time