Domain
PHP (5.2-8.0), Reflection, SPL
Laravel/Lumen, Symfony, Yii, Codeigniter

Engineering
OOP, OOD, Design Patterns, SOLID, DRY, KISS, DDD, Multithreading

Databases
MySQL (indexes, foreign keys, transactions, locks, nested queries, etc)
Redis, Мemcached, MongoDB, ElasticSearch, Kibana

Message brokers
RabbitMQ, Gearman

Tests
Codeception, phpUnit, phpCS, phpMD, A/B testing

Profiling
OpentTracing, Pinba, DataDog

Management
Scrum, Kanban, Waterfall, Jira, Confluence, GitHub/Bitbucket Projects

Version Control Systems
Git (rebase, cherry-pick, tags, stash, squash; RMS: GitHub, Bitbucket, GitLab)
SVN, Mercurial

DevOps
Docker, Vagrant, LAMP, AWS, Ubuntu, Armbian, Bash, SSH, Consul, Teamcity, CIrcleCI, Supervisor