How to implement cache(redis cache) and Async communication in spring boot

Required scenario — when I am trying to get large amount data from db (postgresql) but we are getting API gateways time out issue , so we need to follow

Required scenario

How to implement Async communication in spring boot

step 1- 
use @EnableAsync in class level annotation over service class

@EnableAsync
public class ApprovalItemAsyncServiceImpl {

}
step 2-

use @Async in method level annotation inside service class

@Async
public List<ReportViewForYearModel> readDataFromCache(String startDate, String endDate, UserDetails userDetails) {


step 3

you need to call this method in noraml flow then async method will work 

public class ApprovalItemServiceImpl{

 @Autowired
 private ApprovalItemAsyncServiceImpl approvalAsyncservice;
 
 public void methodCall(){
 approvalAsyncservice.readDataFromCache(startDate, endDate, userDetails);
 }

}

How to implement redis cache in spring boot

we can store data on basis of key and value pair and using key we can get and delete the data.

step 1- 
use @EnableCaching in class level annotation over service class

@EnableCaching
public class ApprovalItemAsyncServiceImpl {}


Step 2 
use RedisTemplate to get method 

 @Autowired
 private RedisTemplate<String, List<?>> redisTemplate;
 
step 3 use

 @Async
 public List<ReportViewForYearModel> readDataFromCache(String startDate, String endDate, UserDetails userDetails) {
  log.info("Inside ApprovalItemAsyncServiceImpl() ::");
  List<ReportViewForYearModel> viewDataList = null;

  SimpleDateFormat formatter = new SimpleDateFormat(CesoaServiceConstants.REQUIRED_DATE_FORMATE_YMD);
  Date beginDate;
  try {
   beginDate = formatter.parse(startDate);
   Date last = formatter.parse(endDate);
   log.info("start reading data from db in method readDataFromCache for user {}" + userDetails.getUserName());
   List<ReportViewForYearModel> viewData = reportViewYearRepo.findByRequestedDateBetweenData(beginDate, last);
   log.info("complite data reading from db  user {}" + userDetails.getUserName());
   // delete on basis of key
   log.info("delete cache data for  user {}" + userDetails.getUserName());
   // delete data from cache (add data into cache)
//   redisTemplate.delete(userDetails.getUserName());

   // put data in cache (add data into cache)
   log.info("put db data in cache for  user {}" + userDetails.getUserName());
   redisTemplate.opsForValue().set(userDetails.getUserName(), viewData);

   // getData from cache
   log.info("get data from  cache for  user {}" + userDetails.getUserName());
   viewDataList = (List<ReportViewForYearModel>) redisTemplate.opsForValue().get(userDetails.getUserName());
   log.info("complite data reding from   cache for  user {}" + userDetails.getUserName());

  } catch (Exception e) {
   log.info("get exception  for  user {}" + userDetails.getUserName(), e.getMessage());
   e.getStackTrace();

  }

  return viewDataList;

 }