package net.notejam.spring;

import java.util.concurrent.Executor;

import org.springframework.aop.interceptor.AsyncUncaughtExceptionHandler;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.orm.jpa.EntityScan;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.EnableAspectJAutoProxy;
import org.springframework.context.annotation.aspectj.EnableSpringConfigured;
import org.springframework.core.convert.ConversionService;
import org.springframework.core.convert.support.DefaultConversionService;
import org.springframework.data.jpa.convert.threeten.Jsr310JpaConverters;
import org.springframework.scheduling.annotation.AsyncConfigurer;
import org.springframework.scheduling.annotation.EnableAsync;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
import org.springframework.web.servlet.LocaleResolver;
import org.springframework.web.servlet.i18n.AcceptHeaderLocaleResolver;

import net.notejam.spring.helper.converter.StringToPeriodConverter;

/**
 * Configures the Spring framework
 *
 * @author markus@malkusch.de
 * @see <a href="bitcoin:1335STSwu9hST4vcMRppEPgENMHD2r1REK">Donations</a>
 */
@SpringBootApplication
@EnableSpringConfigured
@EntityScan(basePackageClasses = { Application.class, Jsr310JpaConverters.class })
@EnableAspectJAutoProxy
public class Application {

    @EnableAsync
    @Configuration
    @EnableScheduling
    public static class AsyncConfiguration implements AsyncConfigurer {

        @Value("${async.queueCapacity}")
        private int queueCapacity;

        @Override
        public Executor getAsyncExecutor() {
            ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
            executor.setMaxPoolSize(Runtime.getRuntime().availableProcessors());
            executor.setQueueCapacity(queueCapacity);
            executor.initialize();
            return executor;
        }

        @Override
        public AsyncUncaughtExceptionHandler getAsyncUncaughtExceptionHandler() {
            return null;
        }

    }

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

    @Bean
    public LocaleResolver localeResolver() {
        return new AcceptHeaderLocaleResolver();
    }

    @Bean
    public ConversionService conversionService() {
        DefaultConversionService service = new DefaultConversionService();
        service.addConverter(new StringToPeriodConverter());
        return service;
    }

}

package net.notejam.spring;

import java.util.concurrent.Executor;

import org.springframework.aop.interceptor.AsyncUncaughtExceptionHandler;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.orm.jpa.EntityScan;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.EnableAspectJAutoProxy;
import org.springframework.context.annotation.aspectj.EnableSpringConfigured;
import org.springframework.core.convert.ConversionService;
import org.springframework.core.convert.support.DefaultConversionService;
import org.springframework.data.jpa.convert.threeten.Jsr310JpaConverters;
import org.springframework.scheduling.annotation.AsyncConfigurer;
import org.springframework.scheduling.annotation.EnableAsync;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
import org.springframework.web.servlet.LocaleResolver;
import org.springframework.web.servlet.i18n.AcceptHeaderLocaleResolver;

import net.notejam.spring.helper.converter.StringToPeriodConverter;

/**
 * Configures the Spring framework
 *
 * @author markus@malkusch.de
 * @see <a href="bitcoin:1335STSwu9hST4vcMRppEPgENMHD2r1REK">Donations</a>
 */
@SpringBootApplication
@EnableSpringConfigured
@EntityScan(basePackageClasses = { Application.class, Jsr310JpaConverters.class })
@EnableAspectJAutoProxy
public class Application {

    @EnableAsync
    @Configuration
    @EnableScheduling
    public static class AsyncConfiguration implements AsyncConfigurer {

        @Value("${async.queueCapacity}")
        private int queueCapacity;

        @Override
        public Executor getAsyncExecutor() {
            ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
            executor.setCorePoolSize(Runtime.getRuntime().availableProcessors());
            executor.setMaxPoolSize(executor.getCorePoolSize() * 2);
            executor.setQueueCapacity(queueCapacity);
            executor.initialize();
            return executor;
        }

        @Override
        public AsyncUncaughtExceptionHandler getAsyncUncaughtExceptionHandler() {
            return null;
        }

    }

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

    @Bean
    public LocaleResolver localeResolver() {
        return new AcceptHeaderLocaleResolver();
    }

    @Bean
    public ConversionService conversionService() {
        DefaultConversionService service = new DefaultConversionService();
        service.addConverter(new StringToPeriodConverter());
        return service;
    }

}

Increase the thread pool