SQLite and indexes

Problem

What becomes confusing, fragile, or impossible without understanding SQLite and indexes? This lesson answers that through explanation, a worked example, two runnable exercises, and a reference solution. No teacher-supplied worksheet is required.

Distributed architectures address concrete capacity, reliability, and coordination limits—but often arrive before those limits do.

Concept explanation

SQLite and indexes belongs to “How far can one machine go?”. SQLite and indexes must be connected to layer below by tracing representation, ownership, control, and failure. One-machine design starts with requirements and estimates, then locates first real bottleneck.

For SQLite and indexes, trace concrete input, state transition, output, and failure through an architecture decision tied to explicit requirements, estimates, state ownership, failure modes, and measured limits.

Start with requirements and estimates, choose the smallest architecture, locate its first bottleneck, then evolve one measured constraint at a time. Apply that model to supplied normal, boundary, and failure cases; each case below names its input and expected evidence.

Example bank

Compare normal, boundary, failure, and cross-layer cases. Predict each observation before revealing the explanation.

Worked example

Start from supplied design.md. Focus: Trace SQLite and indexes end-to-end while running: Design URL shortener in one process with SQLite and explicit backup.

1. Run: Fill design.md, then verify every component traces to one stated requirement or measured constraint.
2. Save baseline evidence. Trace requests, state ownership, capacity, queues, caches, replication, failure domains, recovery, operational load, and cost.
3. Boundary case: At every SQLite and indexes boundary, label owner and representation during: Estimate 10× traffic/storage and index size.
4. Failure case: Locate first layer where evidence diverges during: Crash during write and document recovery procedure.

RESULT
Trace explains Every component traces to requirement; capacity math and load test identify first bottleneck. without skipping any conversion, queue, process, protocol, or storage boundary. Starter-level baseline: Document names one action, target, non-goal, numeric estimate, state owner, request path, bottleneck, and recovery procedure.

Starter material

Create design.md, paste this exact content, then run the command below.

# SQLite and indexes

## Requirements
- One primary user action:
- One reliability target:
- One explicit non-goal:

## Estimate
- Requests/second:
- Stored bytes/day:
- Peak concurrent work:

## Smallest design
- State owner:
- Request path:
- First bottleneck:
- Recovery procedure:

STOP / CLEANUPStop any process started by your slice with Ctrl+C; run git status before leaving.

Independent exercise

Remove one abstraction: SQLite and indexes

1. Create second case from blank file: At every SQLite and indexes boundary, label owner and representation during: Estimate 10× traffic/storage and index size.
2. Then create controlled failure: Locate first layer where evidence diverges during: Crash during write and document recovery procedure.
3. Use Architecture notebook · load tests · traces · Git history to prove behavior, then repair controlled failure.
4. Compare result against supplied acceptance checks and reference approach before marking complete.

Expected result

• Trace explains Every component traces to requirement; capacity math and load test identify first bottleneck. without skipping any conversion, queue, process, protocol, or storage boundary.
• Document names one action, target, non-goal, numeric estimate, state owner, request path, bottleneck, and recovery procedure.
• Controlled SQLite and indexes failure produces captured evidence; repair restores stated invariant without hiding error.

Hints

Solution

Attempt both exercises before opening reference approach.