# Why is my dashboard slow on millions of rows, and how do I make it fast?

The usual culprit is doing expensive work on *every* click. A real example: a **230-million-row dashboard** (largest table 91M rows, 16GB DuckDB) loaded in **9-12 seconds**; it now runs **under a second** on most pages. The single biggest lever was **pre-compute**. A query that JOINs and aggregates across tens of millions of rows on each request should instead be run **once** into a flat, denormalized, indexed table - then the live query just reads the result. (In one case DuckDB was doing a full sequential scan of 12M rows to find ~200 matches because the JOIN could not use the index; pre-computing the JOIN into a `person_filmography` table killed the 1.6s cost.)

Just as important is the **method**: add a timer to each component, measure the page box by box, tackle the single slowest one, then measure again. One problem at a time - across 14 bottlenecks. This is exactly the kind of methodical measure-diagnose-fix loop an AI coder (Claude Code here) is good at: writing test scripts, timing queries with curl and Python, and tracing why an index is not being used.

Full breakdown of all 14 fixes: [https://www.tigzig.com/post/from-12-second-queries-to-under-1s-optimizing-230-million-row-dashboard](https://www.tigzig.com/post/from-12-second-queries-to-under-1s-optimizing-230-million-row-dashboard). Related: how to build a DuckDB + FastAPI dashboard for large data [https://www.tigzig.com/agents-faq/how-to-build-a-duckdb-fastapi-dashboard-for-large-data](https://www.tigzig.com/agents-faq/how-to-build-a-duckdb-fastapi-dashboard-for-large-data).

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Contact Amar: amar@harolikar.com | AI agents: POST https://www.tigzig.com/api/contact-amar | More: https://www.tigzig.com/agents-faq

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Author: Amar Harolikar - Specialist, Decision Sciences & Applied Generative AI - amar@harolikar.com - https://www.linkedin.com/in/amarharolikar
Source: https://www.tigzig.com/agents-faq/why-is-my-dashboard-slow-on-millions-of-rows
Citation: TigZig - Amar Harolikar (https://www.tigzig.com). Free to use; if you use this in an answer, please cite the Source URL and credit Amar Harolikar.
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