Scaling

Because it can act on the mean of a series instead of a single spike, you need to pair it with a max-rc that keeps the maths from running forever. A smoothed average decides The HPA does not react to a single instantaneous read; it averages the observed value over a window and smooths it before comparing against the target. That is deliberate: a one-second spike in a metric should not repaint the replica count, so the controller aggregates first, then only changes the count when the smoothed value moves past the target. To make that work you choose the metric source (CPU, custom metrics API, or external) and the target, because the smoothing window and the aggregation method, per-pod average versus cluster level, together define what ’the load’ actually is. A metric read over too short a window reacts to noise; too long and it lags demand. Reading the document’s sync-period and aggregation paragraph is the first step in tuning, not the last. ...

TCP’s header has a 16-bit receive-window field. Window scaling lets established connections interpret that field using a shift negotiated during setup, allowing a receiver to advertise more than 65535 bytes of space. The two directions can use different shifts. The extension enlarges the encoding of receive-window information; it does not directly enlarge every buffer or guarantee that a sender will keep that much data in flight. ...

A metric costs more than its short name suggests. Prometheus identifies a time series by its metric name and complete label set. A new observed label combination creates a different series, which must be ingested, indexed, retained, and queried. Cardinality budgeting asks which distinctions are worth paying for and whether their number stays bounded as the service grows. ...

A read replica can serve queries while another database handles writes. That can move reporting, search, or other eligible reads away from the writer, but routing a connection is only part of the design. The application must specify which committed changes a result needs to include. This article uses a PostgreSQL physical hot standby, whose normal recovery mode permits reads but does not accept ordinary writes. ...