https://cdelmonte.dev/ Recent content on cdelmonte.dev https://cdelmonte.dev/og-default.png https://cdelmonte.dev/og-default.png Hugo -- 0.147.7 en-us Wed, 10 Jun 2026 00:00:00 +0000 https://cdelmonte.dev/deep-dives/unpacking-parquet-explicit-simd-and-scalar-baselines/ Tue, 09 Jun 2026 00:00:00 +0000 https://cdelmonte.dev/deep-dives/unpacking-parquet-explicit-simd-and-scalar-baselines/ On the JVM, optimizing a hot kernel is not only about writing faster code: it is also about understanding how much the result depends on the machine code HotSpot derives from the scalar loop. Using Parquet bit-unpacking as a concrete case, the piece shows that a SIMD speedup depends on which scalar baseline C2 is handed, when explicit vectorization is actually justified, and why a more specialized scalar routine is not necessarily faster. https://cdelmonte.dev/essays/where-spark-changes-shape/ Tue, 26 May 2026 00:00:00 +0000 https://cdelmonte.dev/essays/where-spark-changes-shape/ Run df.explain on a Parquet scan and you find ColumnarToRow, an operator whose only job is to change the data’s shape. It is the seam where two architectural eras meet, and a record of how portability in analytical systems has relocated from the JVM runtime to the data format and the query plan. https://cdelmonte.dev/deep-dives/the-hidden-dsl-in-catalyst/ Sun, 26 Apr 2026 00:00:00 +0000 https://cdelmonte.dev/deep-dives/the-hidden-dsl-in-catalyst/ How Spark’s internal rewriting framework, Catalyst, exposes an embedded DSL with a public extension surface, the same one Delta Lake and Iceberg use to plug into the optimizer pipeline. https://cdelmonte.dev/deep-dives/delta-explain-making-delta-pruning-visible/ Mon, 13 Apr 2026 00:00:00 +0000 https://cdelmonte.dev/deep-dives/delta-explain-making-delta-pruning-visible/ Partition pruning and data skipping are invisible by default. delta-explain reads the Delta log directly and shows, step by step, how a WHERE predicate narrows down candidate files, with no engine required. https://cdelmonte.dev/deep-dives/anti-patterns-in-catalyst-rules/ Sun, 26 Apr 2026 00:00:00 +0000 https://cdelmonte.dev/deep-dives/anti-patterns-in-catalyst-rules/ Six concrete anti-patterns I encountered building a real Catalyst extension: from the wrong rule type for throws, to mutable state under AQE and Spark Connect, to JVM bootstrap traps in PySpark. https://cdelmonte.dev/essays/the-disaggregation-of-the-lakehouse-stack/ Sun, 08 Mar 2026 00:00:00 +0000 https://cdelmonte.dev/essays/the-disaggregation-of-the-lakehouse-stack/ How Delta Kernel, Arrow, and pluggable execution are disaggregating the lakehouse stack. The lakehouse stack is not converging on a new dominant engine — it is converging on a layered architecture in which protocol, data representation, and query execution are increasingly isolated behind stable interfaces. https://cdelmonte.dev/essays/where-data-system-abstractions-break-semiotic-reading/ Wed, 04 Mar 2026 00:00:00 +0000 https://cdelmonte.dev/essays/where-data-system-abstractions-break-semiotic-reading/ Many of the most surprising performance pathologies in modern data systems are semiotic failures — structural divergences between what an interface signifies and what the underlying system does. https://cdelmonte.dev/essays/delta-lake-merge-at-scale/ Mon, 02 Mar 2026 00:00:00 +0000 https://cdelmonte.dev/essays/delta-lake-merge-at-scale/ At 10 TB, updating 200k rows can mean rewriting thousands of files. Here’s why, and what to do about it. https://cdelmonte.dev/deep-dives/spark-is-not-lazy-spark-compiles-dataflow/ Mon, 03 Nov 2025 00:00:00 +0000 https://cdelmonte.dev/deep-dives/spark-is-not-lazy-spark-compiles-dataflow/ Why calling Spark ’lazy’ is technically reductive, and how thinking of it as a dataflow compiler changes the way you design pipelines. https://cdelmonte.dev/essays/shared-kernel-shared-trust-domain/ Mon, 02 Feb 2026 00:00:00 +0000 https://cdelmonte.dev/essays/shared-kernel-shared-trust-domain/ Containers isolate processes, not trust boundaries. When your platform runs untrusted code, the architectural question is where you place the kernel boundary, and what that costs in memory, latency, and operational complexity. https://cdelmonte.dev/deep-dives/fixing-skewed-nested-joins-spark-asymmetric-salting/ Mon, 01 Dec 2025 00:00:00 +0000 https://cdelmonte.dev/deep-dives/fixing-skewed-nested-joins-spark-asymmetric-salting/ In large-scale Spark pipelines, skew can occur when a single key carries a disproportionately large nested payload. Asymmetric salting offers a targeted solution: explode, salt, join in parallel, and optionally re-aggregate. https://cdelmonte.dev/explainers/parquet-bit-unpacking-explained/ Wed, 10 Jun 2026 00:00:00 +0000 https://cdelmonte.dev/explainers/parquet-bit-unpacking-explained/ Parquet rarely stores a column’s values directly. Dictionary encoding keeps the distinct values once and represents the column through small bit-packed integer indices. This explainer walks through dictionary encoding, how the indices are bit-packed, and the bit-unpacking step that reconstructs them into an int[] before every dictionary lookup. https://cdelmonte.dev/deep-dives/shunting-yard-and-pratt-parsing/ Mon, 06 Oct 2025 00:00:00 +0000 https://cdelmonte.dev/deep-dives/shunting-yard-and-pratt-parsing/ Parsing arithmetic expressions looks simple… until precedence enters the picture. Two classic algorithms — Dijkstra’s Shunting Yard and Pratt’s Top-Down Operator Precedence — provide radically different answers that reveal the same underlying intuition. https://cdelmonte.dev/deep-dives/kubernetes-gcp-service-accounts-workload-identity/ Thu, 01 Aug 2024 00:00:00 +0000 https://cdelmonte.dev/deep-dives/kubernetes-gcp-service-accounts-workload-identity/ GKE Behind the Scenes: Understanding the Interaction Between Kubernetes and GCP Service Accounts Through The Metadata Server. https://cdelmonte.dev/about/ Mon, 01 Jan 0001 00:00:00 +0000 https://cdelmonte.dev/about/ About Christian Del Monte https://cdelmonte.dev/datenschutz/ Mon, 01 Jan 0001 00:00:00 +0000 https://cdelmonte.dev/datenschutz/ Datenschutzerklärung https://cdelmonte.dev/impressum/ Mon, 01 Jan 0001 00:00:00 +0000 https://cdelmonte.dev/impressum/ Impressum https://cdelmonte.dev/selected-work/ Mon, 01 Jan 0001 00:00:00 +0000 https://cdelmonte.dev/selected-work/ Selected articles, talks, and open-source work by Christian Del Monte