- AWS – CodePipeline: Stages, Artifacts and Approvals
A pipeline is stages, and between them an artifact in an S3 bucket — get that one idea and the rest is configuration. Source from GitHub through a CodeStar connection rather than a token, build, a manual approval gate, deploy. Where CodePipeline beats GitHub Actions and where it plainly does not, and the input-artifact mismatch that is the single most common reason a stage fails with nothing useful in the log.
- MongoDB – Spring Data MongoDB
The Java side: repositories versus MongoTemplate, how mapping works, where to declare indexes, and the field rename that catches everyone.
- AWS – CodeDeploy: Blue/Green and Where It Still Fits
CodeDeploy is the piece that takes a built artifact and puts it on the thing that runs it — and in 2026 it earns its place on EC2 and in ECS blue/green, not much elsewhere. The appspec file, the lifecycle hooks in the order they fire, and the validation hook that is the only reason blue/green is safer than in-place. Plus the automatic rollback alarm, and why a deployment can hang for an hour.
- LeetCode 347 – Top K Frequent Elements
The statement contains its own hint: better than O(n log n). That sentence exists to rule out sorting and a max-heap of everything — and the defence that there are usually few unique values is not a complexity argument. A min-heap capped at k works; bucket sort gets it to O(n), because frequencies are small bounded integers you can index by.
- MongoDB – Which Applications Actually Fit
Five shapes of application MongoDB suits well, and four where choosing it is a decision you will be undoing later.