Notes — Module 19: Capstone Project¶

These are your personal build notes and decisions journal. Write freely and honestly. There is no correct format — use whatever helps you think. Return to this file after each milestone to record what you learned and decided.

Module: [[go/19. Capstone Project]] Topic: [[go]] Date started: YYYY-MM-DD Status: In progress Brief chosen: URL shortener / Task API / Webhook runner / Metrics collector (circle one)

Build Log¶

One entry per significant work session. Be specific about what you did and what you learned. Vague entries ("worked on the store") are useless. Specific entries ("fixed a data race in IncrementHits by using UPDATE ... RETURNING instead of SELECT then UPDATE") are valuable.

YYYY-MM-DD — Session 1¶

Milestone: M0 / M1 / M2 / ... What I did: - ...

What surprised me: - ...

Decisions made: - Chose [SQLite / Postgres] because... - Chose [distroless / alpine] as the final Docker base image because...

What I'll tackle next: - ...

Add new session entries here, newest at the top.

Architecture Decisions Journal¶

Record significant design decisions here. For each decision: what you chose, what the alternatives were, and why you chose what you did. This becomes the material for your project README's "design decisions" section.

Decision 1: Storage Backend¶

Date: YYYY-MM-DD What I chose: SQLite / Postgres Alternatives I considered: ... Why I chose this: What I'd change if this were a production system:

Decision 2: Short Code Generation Strategy¶

Date: YYYY-MM-DD What I chose: (random N characters from alphanumeric alphabet / hash-based / sequential counter / ...) Alternatives I considered: ... Why I chose this: Collision handling:

Decision 3: Error Handling Architecture¶

Date: YYYY-MM-DD What I chose: Alternatives I considered: Why I chose this:

Add more decisions as you make them.

Concept Map¶

How the major components of your service relate to each other.

flowchart TD
    Client["HTTP Client"] --> Router["http.ServeMux\n(router.go)"]
    Router --> MW["Middleware Chain\n(logging, timeout, recovery)"]
    MW --> Handler["Handler\n(handler.go)"]
    Handler --> Store["Store interface\n(store.go)"]
    Store --> SQLite["SQLiteStore\n(sqlite.go)"]
    SQLite --> DB[("SQLite DB")]
    Config["Config\n(config.go)"] --> Handler
    Config --> SQLite
    Config --> Server["http.Server\n(main.go)"]

This is a starting point — update it as your architecture evolves.

Key Insights¶

The "aha moments" — discoveries that changed how you think about something.

1. Interfaces enable testing without real dependencies: Fill in when you experience this
2. context.Context is a river, not a bucket: Fill in when cancellation propagation clicks
3. Add insights as you discover them

My Understanding of Key Concepts (After Building)¶

After completing each milestone, explain the concept in your own words based on what you built.

Store Interface (after M1/M2)¶

Your explanation here — how does defining the interface first, before the implementation, change the design process?

What I'm still unsure about: ...

Context Propagation (after M3/M4)¶

Your explanation here — trace one request from r.Context() through middleware into the store.

What I'm still unsure about: ...

Graceful Shutdown (after M6)¶

Your explanation here — what exactly happens between "SIGINT received" and "process exits 0"?

What I'm still unsure about: ...

Connections to Earlier Modules¶

How did each earlier module show up in your project? Be specific.

Questions That Arose¶

Log questions as they appear. Don't stop to answer them now — just capture them. Then move the important ones to QUESTIONS.md.

• ... → added to QUESTIONS.md as Q001
• ...

Code Patterns Worth Remembering¶

Snippets or patterns from your own code that captured something important.

The pattern I'm most proud of¶

// YOUR CODE HERE

Why I'm saving this:

The pattern I wish I had learned earlier¶

// YOUR CODE HERE

Why I'm saving this:

What Tripped Me Up¶

Mistakes I made, misconceptions I had, bugs that cost me more time than they should have.

• The hardest bug: describe it here
• The design decision I'd change: describe it here
• The thing that seemed obvious but wasn't: describe it here

Retrospective (complete after project is done)¶

Write this section only after you have finished the project and graded TEST.md.

What I built:

Time spent (approximate):

What I am proud of:

What I am not satisfied with:

The most important thing I learned:

How my understanding of Go changed:

Last updated: YYYY-MM-DD