Working on a financial module in an ERP application taught me that debugging is not simply about finding an error and changing a line of code. It requires understanding how different parts of an application communicate and how data moves through the system.
During my experience as a Full Stack Developer, I worked with ERP modules involving billing, inventory, CRM, and workflow approvals. One of the areas that helped me understand backend development better was investigating issues in financial transaction workflows.
Here are some lessons I learned from that experience.
1. Understand the Existing Workflow First
When a transaction-related issue occurs, it is tempting to immediately look at the code where the error appears.
However, understanding the complete workflow is more useful.
For example, a typical financial transaction may involve:
- A frontend request containing transaction details.
- A backend API receiving and validating the request.
- Business logic processing the transaction.
- Database operations storing or updating records.
- A response returned to the frontend.
An issue at any stage can affect the final result.
I learned to understand the flow before deciding where the problem might be.
2. Trace the API Request
In a NestJS application, following the request through the backend helps narrow down the source of an issue.
A typical request flow looks like this:
Controller → Service → Database Layer → Response
The controller handles incoming requests, while the service contains the business logic.
When investigating an issue, some useful questions are:
- Is the request reaching the correct endpoint?
- Are the required fields being received?
- Is the validation working as expected?
- Is the service executing the expected logic?
- Is the database operation completing successfully?
For example, if a payment request fails, I would check whether the request reaches the backend, whether the required transaction details are valid, and whether the service successfully completes the database operation.
This helps narrow down whether the issue is related to the API, business logic, or database interaction.
Breaking the workflow into smaller steps makes debugging more systematic.
3. Understand Database Relationships
Financial and ERP applications often involve multiple related entities.
For example, a billing workflow may involve customers, invoices, payments, and transaction records.
Understanding their relationships is important when investigating unexpected results.
Some useful checks include:
- Whether the correct records are being retrieved.
- Whether foreign-key relationships are configured correctly.
- Whether the expected records exist in the database.
- Whether an update is affecting the intended records.
- Whether related data is being fetched correctly.
Working with PostgreSQL also helped me understand the importance of SQL queries when validating application behaviour.
4. Investigate ORM Behaviour
Working with TypeORM introduced me to another important part of backend debugging: understanding how the ORM interacts with the database.
An ORM makes database operations easier to manage, but developers still need to understand what happens behind those operations.
For example, it is useful to investigate:
- Whether entity relationships are configured correctly.
- Whether the expected query is being executed.
- Whether records are being saved or updated correctly.
- Whether the application is handling database errors appropriately.
Understanding both the application logic and the underlying database makes troubleshooting more effective.
5. Validate the Fix Before Considering the Issue Resolved
Finding a possible cause is only one part of debugging.
After making a change, the workflow needs to be validated again.
My validation approach includes:
- Reproducing the original issue.
- Identifying the step where the unexpected behaviour occurs.
- Making the required code change.
- Testing the affected API using Postman.
- Checking the relevant database records.
- Verifying that the expected workflow works correctly.
This is particularly important in financial workflows because an apparently small change can affect related operations.
6. What This Experience Taught Me
Working on production ERP applications helped me understand that effective debugging requires more than familiarity with a programming language.
A few lessons I took away:
- Understand the business workflow before changing the code.
- Trace API requests instead of making assumptions.
- Understand database relationships and data consistency.
- Use logs, API testing, and SQL queries to investigate issues.
- Validate the complete workflow after fixing a defect.
Final Thoughts
Backend debugging becomes easier when the problem is approached systematically.
My experience with NestJS, TypeORM, and PostgreSQL helped me build a better understanding of how APIs, business logic, and databases work together in real applications.
I am continuing to strengthen these skills through practical development and by learning from the problems I encounter.
What is your usual approach when debugging an issue that involves both an API and a database?
I'd love to hear how other developers approach it.
Further Reading
This article is based on my general development experience. Application and business details have been kept confidential.
Top comments (0)