Event sourcing pattern in Kafka - Mini Project: Build & Apply

Event Sourcing Pattern with Kafka

📖 Scenario: You are building a simple event sourcing system using Kafka. Event sourcing means storing all changes as events in order, so you can rebuild the current state anytime by replaying these events.Imagine a bank account where every deposit and withdrawal is an event. We will create events, configure a topic, process events to get the current balance, and finally print the balance.

🎯 Goal: Build a simple Kafka event sourcing example that stores deposit and withdrawal events, processes them to calculate the current balance, and prints the result.

📋 What You'll Learn

Create a list of events with exact deposit and withdrawal amounts

Create a variable for the Kafka topic name

Write a loop to process events and calculate the balance

Print the final balance

💡 Why This Matters

🌍 Real World

Event sourcing is used in banking, e-commerce, and many systems to keep a full history of changes for auditing and rebuilding state.

💼 Career

Understanding event sourcing and Kafka is valuable for backend developers, data engineers, and system architects working with real-time data and distributed systems.

1

Create the list of events

Create a list called events with these exact dictionaries representing bank transactions: {'type': 'deposit', 'amount': 100}, {'type': 'withdrawal', 'amount': 40}, {'type': 'deposit', 'amount': 60}

Kafka

# Create the list of events
# Your code here

Need a hint?

Use a list with dictionaries exactly as shown. Each dictionary has keys 'type' and 'amount'.

2

Set the Kafka topic name

Create a variable called topic_name and set it to the string 'bank_account_events'

Kafka

events = [
    {'type': 'deposit', 'amount': 100},
    {'type': 'withdrawal', 'amount': 40},
    {'type': 'deposit', 'amount': 60}
]
# Set the Kafka topic name
# Your code here

Need a hint?

Assign the exact string 'bank_account_events' to the variable topic_name.

3

Calculate the current balance from events

Create a variable called balance and set it to 0. Then use a for loop with variables event to iterate over events. Inside the loop, if event['type'] is 'deposit', add event['amount'] to balance. If it is 'withdrawal', subtract event['amount'] from balance.

Kafka

events = [
    {'type': 'deposit', 'amount': 100},
    {'type': 'withdrawal', 'amount': 40},
    {'type': 'deposit', 'amount': 60}
]
topic_name = 'bank_account_events'

# Calculate the balance by processing events
# Your code here

Need a hint?

Start balance at 0. Loop through events. Add or subtract amounts based on event type.

4

Print the final balance

Write a print statement to display the text 'Current balance:' followed by the value of balance using an f-string.

Kafka

events = [
    {'type': 'deposit', 'amount': 100},
    {'type': 'withdrawal', 'amount': 40},
    {'type': 'deposit', 'amount': 60}
]
topic_name = 'bank_account_events'

balance = 0
for event in events:
    if event['type'] == 'deposit':
        balance += event['amount']
    elif event['type'] == 'withdrawal':
        balance -= event['amount']

# Print the current balance
# Your code here

Need a hint?

Use print(f"Current balance: {balance}") to show the result.