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17 Backend Engineering Concepts Every Software Engineer Should Understand
From REST APIs and Redis to Kafka, database sharding, and observability — a practical guide to the systems behind modern applications.
A user clicks Place Order.
The frontend sends an HTTP request. The backend authenticates the user, checks inventory, calculates the price, creates an order, processes payment, updates the database, and sends a confirmation.
Everything looks simple from the outside.
But what happens when the user clicks the button twice? What if the payment succeeds but the order service times out? What if a database replica hasn’t received the latest update? What happens when thousands of users place orders simultaneously?
These are the problems backend engineers solve every day.
Understanding frameworks and writing API endpoints is only the beginning. Building reliable backend systems requires understanding communication protocols, caching, asynchronous processing, data consistency, resilience, and observability.
Here are 17 concepts that repeatedly appear in backend engineering interviews and, more importantly, in real production systems.
1. REST APIs and gRPC: How Services Communicate
Applications need a contract that defines how one component communicates with another.
