public void initialFetchAndSchedule() {
    fetchAndUpdateCacheNoThrow();
    if (scheduler != null) {
      scheduler.scheduleAtFixedRate(this::fetchAndUpdateCacheNoThrow, config.updaterPollingIntervalSeconds,
          config.updaterPollingIntervalSeconds, TimeUnit.SECONDS);
      logger.info("Background account updater will fetch accounts from mysql db at intervals of {} seconds",
          config.updaterPollingIntervalSeconds);
    }
    maybeSubscribeChangeTopic(false);
  }
Fetches added or modified accounts and containers from mysql database and schedules to execute periodically.
ambry-account/src/main/java/com/github/ambry/account/CachedAccountService.java