Reconciliation

Idempotency means that performing the same operation multiple times produces the same result as performing it once. This property is critical in automation and distributed systems where network failures or retries may cause a request to be sent more than once. APIs, payment processing, and deployment scripts should be designed to be idempotent so that retries are safe and don't create duplicate side effects.

GitOps is an operational model where Git repositories serve as the single source of truth for both application code and infrastructure configuration. Automated agents like ArgoCD or Flux continuously monitor the repo and synchronize the live environment to match the declared state. Every change goes through pull requests, providing a full audit trail and enabling rollbacks by simply reverting a commit.

A Higher-Order Component (HOC) is an advanced React pattern where a function takes a component as input and returns a new enhanced component with additional props or behavior. Common use cases include adding authentication checks, analytics tracking, or data fetching logic to existing components. While HOCs were a primary code reuse pattern in class-based React, custom hooks have largely replaced them in modern functional component code due to their simpler composition model.

A controlled component is a form element in React whose value is driven by React state rather than the DOM's own internal state. The component's value is set through a `value` prop and updated via an `onChange` handler, giving React full control over the form data. This pattern enables validation on every keystroke, conditional disabling of submit buttons, and enforcing input formats, making it the recommended approach for most form handling in React applications.

Blue-green deployment is a release strategy that maintains two identical production environments — "blue" (current) and "green" (new version). Traffic is switched from blue to green only after the new version passes all health checks, enabling zero-downtime releases. If issues are detected, traffic can be instantly routed back to the blue environment, making rollbacks trivial and fully automated.

Props drilling is the practice of passing data through multiple levels of intermediate components that don't actually use the data themselves, just to get it to a deeply nested child that needs it. This creates tight coupling between components and makes refactoring painful. Common solutions include React's Context API for global-ish state, state management libraries like Zustand or Redux, or component composition patterns that restructure the tree to reduce nesting depth.