Approach: I’d evaluate both query-level fixes (targeted indexes, filters, query rewrites) and architecture-level solutions (partitioning, materialized views, pre-aggregations, denormalized reporting tables), measure with explain plans and query profiling, and pick the mix that balances latency, freshness, and cost.Examples and specific actions:- Indexes (or clustering keys in cloud warehouses) - Add targeted indexes on predicate/join columns or use clustering (BigQuery) / sort keys (Redshift) to reduce scan. - SQL (Postgres example):sql
CREATE INDEX idx_sales_date_customer ON sales(order_date, customer_id);
- Trade-off: faster selective queries, but extra storage and write overhead; many cloud DWs charge by scanned bytes so clustering often better than traditional indexes.- Partitioning - Partition by order_date (daily/monthly) to prune scans for dashboards that use recent ranges.sql
-- BigQuery pseudo
CREATE TABLE sales PARTITION BY DATE(order_date) AS SELECT * FROM raw_sales;
- Trade-off: great for time-bound queries, but too-fine partitions can increase metadata overhead; needs lifecycle management for old partitions.- Materialized views / persisted aggregations - Precompute heavy aggregations (daily sales by region/product). Refresh strategy: incremental or scheduled.sql
CREATE MATERIALIZED VIEW mv_daily_sales AS
SELECT DATE(order_date) d, product_id, SUM(amount) total
FROM sales GROUP BY d, product_id;
- Trade-off: fast reads and low query cost; data staleness unless near-real-time refresh is implemented; storage and refresh compute cost.- Pre-aggregations / OLAP cubes (BI tool or ETL layer) - Build hourly/daily rollups for common dashboard pivots (product × region × channel). Use tools (dbt, Cube.js, Looker PDT). - Trade-off: complexity in maintaining many rollups; best for dashboards with predictable access patterns.- Denormalized reporting tables - Create wide, read-optimized tables joining customer/product dims into sales to avoid expensive joins at runtime.sql
CREATE TABLE rpt_sales AS
SELECT s.*, c.region, p.category FROM sales s
JOIN customers c USING(customer_id) JOIN products p USING(product_id);
- Trade-off: faster reads, simpler SQL; increases storage and write/ETL complexity to keep in sync.Evaluation plan:- Start with query profiling to find hotspots (full scans, expensive joins, GROUP BY).- Apply partitioning/clustering to reduce scanned bytes.- Add materialized views or pre-agg tables for the heaviest aggregates; automate refresh frequency per SLAs.- Use denormalized tables for interactive exploration panels.- Monitor cost (storage, compute, query bytes) and freshness; iterate.Summary trade-offs: indexing/clustering and partitioning reduce scan cost with minimal complexity; materialized views/pre-aggregations give biggest runtime gains but add storage/refresh complexity; denormalization simplifies queries at cost of ETL complexity. Choose based on query patterns, freshness needs, and cloud billing model.