Having experimented with prompts, interacted with APIs, and utilized frameworks to build the core logic of Large Language Model applications, we now turn to the practical considerations involved in developing and deploying these systems effectively. Building a functional prototype is one step; preparing it for sustained use requires attention to structure, security, cost, and operational aspects.

This chapter covers essential practices for taking your LLM application from concept to a more manageable and deployable state. You will learn about:

• Structuring application code for clarity and maintainability.
• Securely managing API keys and other sensitive credentials.
• Strategies for estimating and monitoring the costs associated with LLM API usage.
• Implementing basic caching to optimize performance and reduce expenses.
• Approaches for testing applications that incorporate LLM components.
• An overview of simple deployment options suitable for getting started, such as serverless functions or containerization.

The focus here is on the practical engineering aspects that support the reliable operation of your LLM-driven software.