```
/** Replay tile requests against a size-limited cache of fresh renders. */
export function tileRenders(requests: [number, string][], freshFor: number, size: number): [number, string][] {
  if (!Number.isInteger(freshFor) || freshFor < 1 || !Number.isInteger(size) || size < 1) {
    throw new Error("freshFor and size must be positive integers");
  }
  const held = new Map<string, number>();
  const renders: [number, string][] = [];
  for (const [tick, name] of requests) {
    if (held.has(name)) {
      const lastRenderTick = held.get(name)!;
      if (tick >= lastRenderTick && tick < lastRenderTick + freshFor) {
        continue; // Serve the still-fresh render
      }
    }
    // Make room when full and record one.
    while (held.size >= size) {
      const [oldestName, oldestTick] = held.entries().next().value;
      if (held.size === 1 && oldestTick === tick - freshFor + 1) {
        break; // Tie goes to the name that sorts first
      }
      held.delete(oldestName);
    }
    held.set(name, tick);
    renders.push([tick, name]);
  }
  return renders;
}
```