System requirements

Functional:

List functional requirements for the system (Ask the chat bot for hints if stuck.)...

• Users can view weather for various locations
• Current Location
• Save locations
• Search other locations
• The weather information will be sourced from real-time data: weather stations, satellites, etc.
• Users can save many important locations to their main page
• Emergency weather updates for current location

Non-Functional:

List non-functional requirements for the system...

• Consistency: We want the correct weather, never want to give the user the wrong information. If it stops raining we need that to reflect across all users.
• Usability: Want the app to be simple with easy to read information
• Compatibility: To work with real-time data sources
• Performance: We want the data being shown on the application to reflect the real time data from satellites and weather stations. That data needs to be sent with low latency.
• Scalability: If there is severe weather, there will be more people going on the app to check what is going on and get updates.

Capacity estimation

Estimate the scale of the system you are going to design...

• 50,000 locations
• 1 location = 5 KB
• The weather for each location is updated 2 times a day: morning and night
• 100,000 users
• Each user reads the weather for a location two times a day

Writes/day:

50,000 locations, each location holds 5KB of data, and that's updated 2 times a day

50,000*5KB*2/day = 100,000KB writes/day

= 100 MB/day

Reads/day:

100,000 users, reading the weather 2 times a day

100,000*5 KB*2 = 1,000,000 KB reads/day

= 1 GB/day

API design

Define what APIs are expected from the system...

User API:

getweather(location) - Will get and display the weather for a given location.

setfavorite(location) - Will allow users to add various locations to their 'favorites' list.

searchlocation(location) - Will allow users to search for new locations.

listlocations(favorites) - Will be a feed that will list the user's saved locations weather reports.

getLocation(current_location) - will get the user's location to populate the weather for their current location.

Weather Data API:

realtime_update(location) - will update the weather at a location

send_alert(location) - will update the database and send an alert to the location with severe weather and all users in that current location.

Database design

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...

SQL database

• While it isn't necessarily important that the data is relational, it is important that the data is consistent and SQL databases can help with this.

Users Table

• id, current_location, favorited_locations

Locations Table

• id, city_name, state_name, zipcode, weather_id

Weather Table

• id: {day: temperature, rain_percentage, wind_speed, cloud_percentage, humidity}

Users will have their current location if allowed and then also a list of favorited locations they can add through searching

When searching for locations, users will query the locations table. When searching the weather at a specific location, the locations table will refer to the weather table which will contain all the data regarding the weather at that location on various days

High-level design

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...

• Real time weather sources will populate our weather database with relevant information, updating twice a day: early mornings and late evenings

• The locations database will talk to the weather database to populate information

• User's current location will update automatically through gps

• When user's search for new locations, they will look through the locations database. If favorited, it will be added to their list of favorite locations and the weather will be shown now in their homepage under their current location

Request flows

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...

Detailed component design

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...

Trade offs/Tech choices

Explain any trade offs you have made and why you made certain tech choices...

• Trading Availability for Consistency. While availability is important, consistency is more important.We don't want to show users incorrect information.
• SQl over no-sql. While no-sql is easier and faster, we want consistency and strong ACID principles which a sql database can give us.

Failure scenarios/bottlenecks

Try to discuss as many failure scenarios/bottlenecks as possible.

Future improvements

What are some future improvements you would make? How would you mitigate the failure scenario(s) you described above?