```ts
/** An append-only log of timestamped events. */
export class EventLog<T extends Event> {
  private #events: T[] = [];

  /** Append one event. */
  record(event: T): void {
    this.#events.push(event);
  }

  /** Every event at or after the given timestamp, in insertion order. */
  since(timestamp: number): T[] {
    return this.#events.filter((event) => event.timestamp >= timestamp);
  }
}
```