System requirements

Functional:

• The system should have a user-friendly interface
• The users can swap their shifts with colleagues according to the schedule
• The user may choose the appropriate shift in the shift calendar and mark it. Their colleagues approve or disapprove it. Their manager should review changes.
• The users can change the shift two months in advance
• If the manager approves a shift the user swapped.
• The users can get the history of their shift swap.

Non-Functional:

• The system guarantees compliance with labor laws and fairness measures to prevent favoritism and unequal shift distribution.
• The system has mobile and web clients
• If the user changes the shift in the calendar, they will be notified by colleagues within 100 milliseconds.
• The system stores the shift history for one year.
• The users can see only the other shifts approved by a manager.
•  The system should be able to handle a large number of users.
• The system should be reliable and available even under high load.

API design

Define what APIs are expected from the system...

Here's a breakdown of the essential REST API for our Employee Swap System.

User service:

PUT /auth/login - authenticate a user

PUT /auth/logout - log out user

POST /auth/register - register new user:

{ "name": "name1"

"email":....

"phone": ...

"employe_id":

"position":

"department":

"manager_id"

}

Employee shift matching service:

PUT /shift_matching/{employee_id1}/{shift_id1}/swap/{employee_id2}/{shift_id2} - try to swap the shift_id1 of the employee_id1 with shift_id2 of employee_id2:

Return :

{ "swap_id"....

"status": IN_PROGRESS,APPROVED_BY_MANAGER,APPROVED_BY_EMPLOYEE,CANCELED

"createdAt": ....

}

GET /shift_matching/{employee_id1}/status/{shift_id} - return the shift attempt status:

{ "swap_id"....

"status": IN_PROGRESS,APPROVED_BY_MANAGER,APPROVED_BY_EMPLOYEE,CANCELED

"createdAt": ....

}

PUT /employee_shift/{emploey_id}/approve/{shift_id} - an employee approves the suggested shift.

PUT /employee_shift/manager/{manager_id}/approve/{shift_id} - a manager approves the suggested shift if both employees agree.

Employee Shift service:

GET /employee_shift/{empoyee_id}/shifts - get the list of the shifts schedule by the employee_id:

{ "employee_id":...

"shifts":[

{ "shift_id":....

"startFrom":

"endTo":

},

....

]

GET /employee_shift?dateFrom=&dateTo=&offset=&size= - get the full shifts for the given time interval:

{

"date": ...

[{

"shift_id": ...

"employee_id": ....

"startFrom":

"endTo":...

}, ...]

}

High-level design

See the diagram from the high-level architecture.

API Gateway provides DDoS protection and TLS termination, and routes the requests to the right service nodes.

The user service:

• log in the user and assign them a new JWT.
• log out the user
• register new user

Employee shift matching service:

• query the current employee shifts to swap them. If both employees agree to swap their shifts, it sends the approval to their manager.
• Query the current status of the shift swap
• If the employee's shifts are changed, it sends the updated shift event to Kafka to be received by the Employee shift service.

Employee shift service:

• store the shift information in Postgres
• receive the updated shift event from Kafka and store the updated shift information to Postgres
• return the shift for employee_id or for all employees

Kafka:

• event streaming platform to process the shift update events.

Postgres:

• Hold the user and shift information

Redis:

• cache the employee shift information

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...

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...