- AWS – CodeBuild: buildspec, Caching and Build Speed
The buildspec file phase by phase, what each one is actually for, and the artifacts block that decides what the next stage receives. Then the two things that make builds slow and expensive: no dependency cache, and a compute type chosen by guessing. Local caching versus S3 caching, environment variables that should be parameter references, and privileged mode for building a container image.
- 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.