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List functional requirements for the system (Ask the chat bot for hints if stuck.)...
List non-functional requirements for the system...
Estimate the scale of the system you are going to design...
Define what APIs are expected from the system...
We will not use REST API, will opt for websocket instead. Because it's a real-time chat app that requires two-way communication, if we consider Rest API and send a POST and GET request every time the user wants to send and receive a message, it will create a lot of overload on the servers.
Defining the system data model early on will clarify how data will flow among different components of the system. Also you could draw an ER diagram using the diagramming tool to enhance your design...
User DB:
We need a user database to store user info including user_id, name, email..etc.
Chat DB:
We need a time series database to store content of the messages, the structure will be id, timestamp, format (enum: text, picture, video), text_content, link (if it is picture/video, we need to store them in a BLOB storage and link it to the metadata DB). Opting for time series database because for chat messages, there will be a lot of reads and writes, and they should be displayed by the timestamp and time series database offers us a easy way to fetch messages over time period as well as providing support for high volume of reads and writes with low latency. On top of that, we don't need to consider transaction as it is chat and it's ok if we see duplicate messages once in a while, meaning relational database isn't necessary here.
BLOB Storage:
We can use BLOB storage such as Amazon S3 to store the media files linked in chat
You should identify enough components that are needed to solve the actual problem from end to end. Also remember to draw a block diagram using the diagramming tool to augment your design. If you are unfamiliar with the tool, you can simply describe your design to the chat bot and ask it to generate a starter diagram for you to modify...
Explain how the request flows from end to end in your high level design. Also you could draw a sequence diagram using the diagramming tool to enhance your explanation...
Dig deeper into 2-3 components and explain in detail how they work. For example, how well does each component scale? Any relevant algorithm or data structure you like to use for a component? Also you could draw a diagram using the diagramming tool to enhance your design...
Explain any trade offs you have made and why you made certain tech choices...
Try to discuss as many failure scenarios/bottlenecks as possible.
What are some future improvements you would make? How would you mitigate the failure scenario(s) you described above?