                         /---\                                                                                               
                         \___/                                                                                               
              ---------------------------                                                                                    
                       Customer                                                                                              
                 |                                                                                                           
                 | E-Commerce System                                                                                         
+-------------browses----------------------------------+                                                                     
|                |                                     |                                                                     
|                v                                     |                                                                     
|             +--------------------------+             |                                                                     
|             |     Web Application      |             |                                                                     
|             |                          |             |                                                                     
|             +--------------------------+             |                                                                     
|                |                                     |                                                                     
|              calls                                   |                                                                     
|                |                                     |                                                                     
|                v                                     |                                                                     
|             +--------------------------+             |                                                                     
|             |       API Gateway        |             |                                                                     
|             |                          |             |                                                                     
|             +--------------------------+             |                                                                     
|                |     |     |                         |                                                                     
|                |     |     |                         |                               external                              
|          reads/writes|     +------------------------sends notifications------------------------+--------------------------+
|                |     +----------processes payments-----------+                                 |                          |
|                |                                     |  |    |                                 |                          |
|                v                                     |  |    v                                 v                          |
|              .----------------------.                |  |  +-------------------------+       +--------------------------+ |
|             |\-____________________-/|               |  |  |    Payment Provider     |       |      Email Service       | |
|              \-______Database______-/                |  |  |                         |       |                          | |
|                                                      |  |  +-------------------------+       +--------------------------+ |
|                                                      |  |                                                                 |
+------------------------------------------------------+  +-----------------------------------------------------------------+
