Read a PostgreSQL query plan without getting lost
Follow the work through a query plan, compare estimates with actual rows, and learn what to investigate before adding another index.
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Practical answers. Deeper understanding. Find your next database breakthrough.
MySQL composite indexes: why column order matters
Build an index around a real access pattern, then use EXPLAIN to understand what it helps—and what it doesn't.
Window functions: keep the rows, add the context
Calculate a running total and rank orders within each customer without collapsing the underlying rows.
Cache-aside with Redis: the easy part is the lookup
Follow a cache hit and miss, then work through invalidation, stale data, and the race conditions hiding between them.
Expiration and eviction are two different promises
A TTL controls freshness over time. An eviction policy controls what happens under memory pressure. Your cache needs both decisions.
MongoDB: embed the data you read together
Choose document boundaries from access patterns, growth, and update behavior rather than translating relational tables one-for-one.
Your first MongoDB aggregation pipeline
Filter paid orders, group revenue by customer, and sort the result using a small dataset you can inspect by hand.
Analyze a Parquet file with DuckDB and SQL
Go from a local file to a useful analytical query without standing up a database server.
A transaction is a boundary, not a magic shield
Separate atomicity from isolation and learn why two individually correct transactions can still surprise each other.
OLTP and OLAP: two workloads, different priorities
Understand why checking out a shopping basket and analyzing a year of sales ask very different things of a database.
Design DynamoDB keys from the questions you need to ask
Start with one application's reads and writes, then choose partition and sort keys that make those operations direct.
RDS availability is not a backup strategy
Separate failover, read scaling, and point-in-time recovery before choosing your managed database configuration.