Tag
aggregation
- May 21, 2026 Window Assignment and Trigger Semantics How an event is mapped to windows, why sliding windows multiply state, and how triggers separate when a result is emitted from what it contains. data engineering
- May 1, 2026 Batching and the Amortization of Per-Item Cost How grouping work converts a fixed per-operation cost into a per-batch cost, where the delay comes from, and why batch size is a throughput constraint rather than a tuning knob. performance engineering
- Mar 6, 2026 Histogram Buckets, the +Inf Bucket, and How Quantiles Are Interpolated Why histograms store counts per bucket rather than values, how cumulative bucket counts make merging trivial, and what linear interpolation inside a bucket assumes about the distribution. observability
- Dec 30, 2025 Fleet-Wide Alerting and the Per-Instance Rule Why the aggregation level of an alerting rule decides both what it can detect and how many notifications it produces, and how to choose between per-instance, per-shard, and fleet-wide evaluation. observability
- Nov 1, 2025 Averaging Ratios and the Geometric Mean in Composite Scores Why the arithmetic mean of normalised ratios depends on the reference machine, when the geometric mean is the right summary, and where the harmonic mean is forced by the arithmetic of rates. performance engineering
- Oct 4, 2025 A-MPDU Aggregation and Block Acknowledgement How 802.11n packs many frames into one transmission, why each subframe keeps its own check sequence, and what the block ack bitmap window buys. networking
- Sep 18, 2025 Merging Profiles Across a Fleet Without Losing the Tail Why summing per-host profiles answers a different question than profiling the fleet, how weight normalization changes the answer, and what a merged profile cannot tell you. observability
- Apr 28, 2025 Hierarchical Heartbeat Aggregation and the Cost of Intermediate Levels Why a tree of monitors cuts liveness traffic from quadratic to linear, what the extra level adds to detection time, and how the aggregate view loses the identity of the observer. distributed systems
- Oct 5, 2024 Composite Objectives: Compressing Multi-Signal Health into a Single Score How normalization, weighting, and aggregation order determine what a composite objective means, and why the same weights can hide opposite failure patterns. observability
- Oct 3, 2024 Sliding Windows and Exponential Histograms for Recent Data Why a window over the last W items needs a different summary from a whole-stream sketch, how bucket merging bounds error to a constant factor, and what late-arriving data does to the guarantee. algorithms
- Sep 22, 2024 Folded Stacks, Call Trees, and What Aggregation Destroys Two representations of the same samples, what each preserves, and why the choice determines whether a profile can be merged across hosts or read as a flame graph. observability
- Jan 24, 2024 Delta and Cumulative Temporality in Collection Pipelines How the two ways of reporting a sum interact with resets, why one is cheaper to transmit and the other cheaper to align, and how a pipeline converts between them without losing increments. observability
- Sep 6, 2023 Counting Distinct Values Without Storing Every Record How log-frequency analysis uses register-based sketches, what the relative error formula implies for sizing, and when an exact set is the cheaper answer. observability
- Jul 7, 2023 Aggregation Laws: Which Metric Operations Commute Why sums, counts, minimums and maximums survive regrouping while averages and percentiles do not, and how the order of rate and sum changes the answer. observability
- Aug 17, 2022 Aggregating Percentiles Across a Fleet Without Losing the Tail Why per-host percentiles cannot be combined directly, how cumulative bucketed histograms make merging exact, and what temporal aggregation does to the tail that spatial aggregation does not. performance engineering
- Aug 7, 2022 Hot Keys, Skew, and Load Imbalance in Hash Partitioning Why a partitioner that distributes keys evenly can still produce one task with sixty times the average work, and the static and sampled fixes that spread that load. data engineering
- Jul 27, 2022 Grouping, Duplicate Elimination, and Grouping Sets What a GROUP BY actually computes, how the sort-based and hash-based forms differ in output order, and how ROLLUP and CUBE collapse into one scan. databases
- Apr 22, 2022 Atomics and Contention in Counters and Aggregates Why a single global atomic counter serialises a kernel, how per-warp and per-block aggregation cuts that traffic, and which failure modes survive the optimisation. gpu computing
- Feb 19, 2022 In-Kernel Aggregation: Counting Stacks in a Hash Map Instead of Shipping Them How a kernel-side profiler folds samples into a map before userspace sees them, why that removes the ring buffer from the hot path, and where the map's limits bite. observability