Step 01 of 06
Learn the concept
Memory is fast and forgetful. A service that forgets every outage on restart is a goldfish with a PID. SQLite gives Beacon durable history without asking the learner for a database server or a cloud account.
The ideas this is made of
Embedded does not mean toy
SQLite is a database library linked into the process, not a separate server. It is excellent for one service writing local state, which is exactly this course. The trade-off is topology: multiple machines do not magically share a file. That is fine here. Course four will give the file a persistent volume.
Migrations are source control for schema
A migration is an ordered change such as 001_create_results.sql. Startup applies missing migrations and records that they ran. This matters because databases outlive binaries. Without migrations, every deploy depends on someone remembering the right manual SQL at the worst possible time.
Indexes should match questions
Beacon will ask for recent results by target and time. An index on (target, checked_at) helps that query and has a cost on writes. Indexing every column is not thoroughness; it is tax collection. Name the query first, then add the index that serves it.
Pure Go matters when images arrive
The modernc.org/sqlite driver avoids cgo. That means later container builds do not need a C compiler, libc headers or platform-specific cross-compilation tricks. The import path is unusual, but the payoff is a smaller, simpler build pipeline in the packaging course.
package main
import (
"database/sql"
"fmt"
_ "modernc.org/sqlite"
)
func main() {
db, err := sql.Open("sqlite", "file:example.db?mode=memory&cache=shared")
if err != nil { panic(err) }
defer db.Close()
_, err = db.Exec("create table checks (target text, ok integer)")
fmt.Println(err == nil)
}The blank import registers the SQLite driver with database/sql. Beacon will use a real file path, but an in-memory database keeps the mechanism visible.
Persistence choices
| Store | Strength | Limit |
|---|---|---|
Memory | Fast snapshots | Lost on restart |
SQLite | Local durable file | One-node storage |
Postgres | Shared service | Needs server/account |
JSON file | Readable | Hard to query safely |
What these are called on the job
Migration — An ordered, repeatable database schema change.
Index — A data structure that speeds selected reads while adding write cost.
Transaction — A group of database operations committed together or rolled back together.