Topic
MongoDBAdvancedSeven ordered questions that decide embed, reference or a hybrid, the mechanical cost of each choice, and a help desk schema worked through end to end.
#data-modeling#nosql#schema-design
SQLSTATE 40001 is how serializable isolation stays correct in a distributed database. Add client-side retries, cut contention, and know when READ COMMITTED fits.
#concurrency#transactions#troubleshooting
PostgreSQLIntermediateA session doing nothing can stop VACUUM from cleaning every table and stall your next migration. Find them, kill them safely and prevent them with the right timeouts.
#maintenance#mvcc#transactions
PostgreSQLIntermediateA reference comparison of PostgreSQL and MySQL: storage and MVCC, isolation defaults, DDL, data types, indexes, replication, licensing and tooling, with a decision summary.
#indexing#internals#replication
SQLiteBeginnerWhat WAL mode changes compared with the default rollback journal, what it costs, when not to use it, and how to turn it on, check it and switch back.
#concurrency#configuration#transactions
MySQLIntermediateError 1205 on a simple UPDATE, from code that doesn't even use transactions. Find the blocking session, spot the missing index that's locking too much and stop it coming back.
#locking#transactions#troubleshooting
SQL ServerBeginnerA 200 GB .ldf for a 20 GB database? Shrinking only treats the symptom. log_reuse_wait_desc tells you the real cause, and here's how to fix each one.
#maintenance#transactions#troubleshooting
SQL ServerIntermediateNOLOCK doesn't just risk dirty reads. It can skip rows, count rows twice and fail with error 601. Read Committed Snapshot Isolation removes the blocking without the wrong answers.
#concurrency#locking#transactions
GeneralIntermediateSelect-then-insert breaks under concurrency. Use a unique constraint plus one atomic statement: ON CONFLICT, ON DUPLICATE KEY UPDATE, or UPDLOCK/SERIALIZABLE in SQL Server.
#concurrency#schema-design#transactions
SQL ServerIntermediateWhat each isolation level protects you from, what it costs, and why so many teams switch on READ_COMMITTED_SNAPSHOT.
#concurrency#locking#transactions
