We use Django application, and we use it's DB file for e-mail aliases.

The settings are by conf.d/router/402_exim4-config_virtual_sql.

# members@fsij.org
fsij_members:
  driver = redirect
  domains = fsij.org
  condition = ${if eq {$local_part}{members}{yes}{no}}
  forbid_pipe
  forbid_file
  data = ${lookup sqlite {/home/fsij/django/fsij/fsij.db \
           select email from auth_user, auth_user_groups, auth_group \
           where auth_user_groups.group_id = auth_group.id \
               and auth_user.id = auth_user_groups.user_id \
               and auth_group.name = 'fsijMember';} \
           {$value}fail}
  errors_to = $local_part-request@fsij.org
  no_more

# board@fsij.org
fsij_board:
  driver = redirect
  domains = fsij.org
  condition = ${if eq {$local_part}{board}{yes}{no}}
  forbid_pipe
  forbid_file
  data = ${lookup sqlite {/home/fsij/django/fsij/fsij.db \
           select email from auth_user, auth_user_groups, auth_group \
           where auth_user_groups.group_id = auth_group.id \
               and auth_user.id = auth_user_groups.user_id \
               and auth_group.name = 'boardMember';} \
           {$value}fail}
  errors_to = $local_part-request@fsij.org
  no_more

# Lastly, <user>@fsij.org
virtual_sql_fsij:
  driver = redirect
  domains = fsij.org
  data = ${lookup sqlite {/home/fsij/django/fsij/fsij.db \
           select email from auth_user where username='$local_part';} \
           {$value}fail}
  no_more