What is technical debt (Code Debt) and how to work with it?

Technical Debt — is a metaphor reflecting compromises in development, where a short-term solution is chosen at the expense of long-term maintainability, flexibility, or architectural integrity of the code. Essentially, it is a debt that must be repaid with subsequent efforts (refactoring, rework) through more complex modifications or bug fixes in the future.

Types of technical debt:

• Deliberate: Taken consciously, for example, to quickly release an MVP or meet tight deadlines.
• Inadvertent: Arises due to lack of experience, insufficient time for learning, poor planning, or lack of proper quality control.

Reasons for occurrence:

• Tight development schedules.
• Inexperience of the team.
• Lack of clear requirements or frequent changes.
• Weak architecture planning.
• Insufficient testing.
• Insufficient or outdated documentation.

How to work with technical debt:

• Identify: Regularly analyze code (Code Review, static analyzers, metrics).
• Prioritize: Assess debt based on impact on business, risks, and correction complexity. Use a priority matrix.
• Plan: Allocate time for debt repayment in sprints or special iterations ("refactoring sprints").
• Repay: Conduct refactoring, improve tests, update documentation. Do this in small, manageable steps.
• Prevent: Implement best engineering practices: TDD, CI/CD, Code Review, strict coding standards, pair programming. Train the team.

Examples of working with debt:

• Refactoring complex and frequently changing modules.
• Writing tests for code sections with low coverage.
• Removing unused code.
• Updating dependencies.

// Example of refactoring a function with technical debt (logic duplication)
def calculate_discount_old(price, user_type):
    if user_type == "premium":
        discount = price * 0.15
    elif user_type == "vip":
        discount = price * 0.25
    else:
        discount = price * 0.05
    return price - discount

def apply_coupon_old(price, coupon_code):
    if coupon_code == "SAVE10":
        discount = price * 0.10
    elif coupon_code == "SAVE20":
        discount = price * 0.20
    else:
        discount = 0
    return price - discount

// Refactoring: extracting common discount calculation logic
def apply_discount(price, discount_rate):
    return price * (1 - discount_rate)

def calculate_discount(price, user_type):
    discounts = {
        "premium": 0.15,
        "vip": 0.25
    }
    rate = discounts.get(user_type, 0.05)
    return apply_discount(price, rate)

def apply_coupon(price, coupon_code):
    coupon_rates = {
        "SAVE10": 0.10,
        "SAVE20": 0.20
    }
    rate = coupon_rates.get(coupon_code, 0)
    return apply_discount(price, rate)

// This example demonstrates how to extract the common logic
// apply_discount and use dictionaries to manage
// discount and coupon rates instead of if/elif chains.
// This makes the code more readable, extendable, and less error-prone.

Constant management of technical debt is an important part of the software development lifecycle and helps maintain the health of the project.