Introduction

Every product engineer eventually asks the same three questions: which data store, which compute shape, which model. Left to per-team taste, the answers drift - one service reaches for MongoDB because someone liked it last job, another stands up a Redis cluster "just in case," a third calls the frontier model for a task a fast tier would handle. Cogitave answers all three with a directive guidance system instead: a decision guide that tells you the default, walks you through a real decision tree, and states exactly when - and how - you are allowed to choose something else.

Three guides exist today, one per selection domain:

• Database selection - which operational data store for a workload.
• Infrastructure selection - which compute, storage, messaging, caching, or edge shape for a workload.
• Model selection - which model capability tier to call for a task.

All three are governed by one decision: ADR-0021, which places them as a selection layer sitting above the technology radar's Adopt/Trial/Assess/Hold rings and above the domain standards that say how to build once a choice is made.

Why this matters

A guidance system only earns its name if you actually use it: read the default, walk the tree in order, and - if you must deviate - record the measured need in an ADR rather than defaulting from memory or habit. This module teaches you to do exactly that, and it is the last module in the "Patterns and golden paths" learning path: finishing it completes the path and earns its trophy.

What you will get from this module

Not a summary of three standards to memorize, but the ability to open any of the three guides cold, find its default, walk its decision tree for a real workload or task, and know precisely what a deviation must record before it is justified.