- AWS – API Gateway: HTTP APIs, Routes and Custom Domains
HTTP API or REST API — one table, and for most backends the answer is the cheaper, faster one. Routes, proxy integration and the event shape your handler receives, CORS as configuration rather than code, and authorizers. Then the stage trap that makes one of your two URLs 404 forever: a named stage prefixes every path while a custom domain does not, and `$default` is the way out.
- LeetCode 145 – Binary Tree Postorder Traversal
The hardest traversal to write iteratively, and the standard answer avoids writing it at all: postorder reversed is node-right-left, which is preorder with the children swapped. Two lines changed and every awkwardness disappears — plus what it costs when you genuinely need it bottom-up.
- MySQL – The Binary Log
The log that makes replication and point-in-time recovery possible. What the binlog records and what it does not, ROW versus STATEMENT versus MIXED format and why ROW is the default now, reading one with mysqlbinlog, finding the statement that deleted the rows, replaying up to a position or a timestamp to recover, expire_logs_days and the disk it fills if you forget.
- LeetCode 144 – Binary Tree Preorder Traversal
The easiest of the three traversals to write iteratively, and worth doing right after inorder because the contrast explains why: a preorder node is emitted the moment you arrive, so there is nothing to come back for. Push right before left, since a stack reverses what you give it.
- MySQL – Backup and Restore with mysqldump
Taking a backup you can actually restore from. mysqldump for one database, several, or all, --single-transaction and why omitting it locks your tables, schema-only and data-only dumps, --routines and --events which are NOT included by default, restoring, why a dump is a logical backup and what that costs at size, and the only test that matters — restoring it somewhere and looking.