Spring Batch - Executing multiple instances of a job at same time

Yes you can. Spring Batch distinguishes jobs based on the JobParameters. So if you always pass different JobParameters to the same job, you will have multiple instances of the same job running. A simple way is just to add a UUID parameter to each request to start a job. Example:

final JobParametersBuilder jobParametersBuilder = new JobParametersBuilder();
jobParametersBuilder.addString("instance_id", UUID.randomUUID().toString(), true);
jobLauncher.run(job,jobParametersBuilder.toJobParameters());

The boolean 'true' at the end signal to Spring Batch to use that parameter as part of the 'identity' of the instance of the job, so you will always get new instances with each 'run' of the job.