private void processAccountJsonFile() {
    if (accountFile == null) {
      return;
    }

    try {
      if (!Files.exists(accountFile)) {
        logger.warn("JSON account file '{}' does not exist", accountFile.toAbsolutePath());
        return;
      }
      String accountsJsonString = new String(Files.readAllBytes(accountFile), StandardCharsets.UTF_8);
      AccountInfoMap newAccountInfoMap = new AccountInfoMap(accountsJsonString);
      accountInfoMapRef.set(newAccountInfoMap);
    } catch (Exception e) {
      logger.error("Failed updating accounts", e);
    }
  }
Loads initial accounts into memory via a JSON file.
ambry-account/src/main/java/com/github/ambry/account/InMemoryAccountService.java