A place to start
A query can return plausible numbers and still answer the wrong question. Start with the result grain, make ordering and window frames explicit, and inspect the plan before adding an index. For concurrent writes, work through the anomaly your transaction must prevent.
Practical guide
Worked PostgreSQL examples for running totals, stable rankings, peer rows, and explicit window frames.
Read the guide →Practical guide
Choose PostgreSQL indexes from actual filters, ordering, selectivity, and EXPLAIN output instead of indexing every column.
Read the guide →Practical guide
A concurrent counter example shows why transactions alone do not prevent lost updates and when to use atomic or conditional writes.
Read the guide →Make cache behavior, retries, and response headers explicit before your endpoint reaches production.
02Ground answers in compact reference data, validate the shape, and measure the failures.
04Find files, recover Git work, and write shell commands that handle real filenames.
05Build usable layouts, keyboard interactions, text search, and time handling.
06Connect service signals, background jobs, probability, and experiment design to real decisions.
