# Fixed-step work without overlapping ticks

> Documentation for Redweb 0.13.2. Install that exact version when following these examples.

FixedStepService compensates for scheduler drift, bounds catch-up, contains async failures, and reports lag that was deliberately dropped.

This pattern demonstrates one API area. Application-specific names, credentials, assets, and policies may need to be supplied. Complete starter recipes include all required application files.

```js
const { FixedStepService, SocketRoute } = require('redweb')

class Simulation extends FixedStepService {
  constructor() {
    super('simulation', 50, 3, 250)
  }

  async onTick(stepMs, tick) {
    await authoritativeGame.update(stepMs, tick)
  }

  onLagDropped(milliseconds) {
    console.warn('Simulation lag discarded', { milliseconds })
  }
}

class SimulationRoute extends SocketRoute {
  constructor() {
    super({
      path: '/simulation',
      handlers: [InputHandler],
      services: [Simulation],
    })
  }
}
```

## Notes and boundaries

- The active async tick must finish before another begins.
- maxCatchUpTicks prevents a spiral of death.
- maxRetainedLagMs bounds remembered delay.