93 articles · 35 databases · 63 topics
Practical tutorials, performance tuning and internals for SQL Server, PostgreSQL, MySQL, MongoDB, Redis and every engine in between — written by people who run them in production.
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RelationalMicrosoft's enterprise relational database engine.
27 articles →
RelationalThe world's most advanced open-source relational database.
6 articles →
RelationalThe popular open-source database behind much of the web.
7 articles →
RelationalThe long-standing heavyweight of enterprise data.
9 articles →
EmbeddedA tiny, serverless SQL engine inside everything.
4 articles →
DocumentA document database built around flexible JSON-like documents.
6 articles →
Key-valueIn-memory data structures at microsecond speed.
1 article →
Wide-columnMasterless, linearly scalable wide-column store.
3 articles →
Editor's picks
SQL ServerIntermediateSame proc, same code, suddenly 100× slower, and fast again when you run it in SSMS. Here's how parameter sniffing causes it, how to prove it and the fixes that actually hold.
In this article
· 8 min read
SQLiteBeginnerStill getting SQLITE_BUSY with a timeout set? The default timeout is zero and deferred transactions can't wait. WAL mode, busy_timeout and BEGIN IMMEDIATE fix most cases.
#concurrency#locking#troubleshooting
PostgreSQLIntermediateMVCC means Postgres doesn't store a row count. Make exact counts cheaper, get instant estimates from the planner, and keep exact counters when you really need them.
#internals#mvcc#performance
Fresh commits
SQLiteIntermediateWhat SQLITE_BUSY means, where it is returned in rollback-journal and WAL mode, why a timeout sometimes does nothing, the extended codes, and how to find who holds the lock.
#concurrency#internals#locking
GeneralIntermediateAdjacency lists, materialized paths, nested sets and closure tables compared, and why a parent_id column plus a recursive CTE is the right default.
#data-modeling#schema-design
ElasticsearchIntermediateYellow means missing replicas and red means missing primaries. Use the allocation explain API to find the exact cause: replica count, disk watermarks, allocation filters or failed retries.
#configuration#nosql#troubleshooting
MongoDBIntermediateThe 100 MB blocking-sort limit means your index doesn't provide the sort order. Build compound indexes with the ESR rule, order pipeline stages correctly, and know when allowDiskUse is fine.
#indexing#nosql#performance
Oracle DatabaseIntermediateYour long query needed undo that was already overwritten. How Oracle read consistency uses undo, how to read V$UNDOSTAT, and why committing inside a loop causes it.
#configuration#mvcc#troubleshooting
Learning paths
LEVEL 01
Tables, keys, joins and your first indexes. Build intuition that lasts.
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LEVEL 02
Query plans, transactions, replication and schema design trade-offs.
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LEVEL 03
Storage engines, concurrency control, internals and extreme tuning.
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