+ Solr or Elasticsearch
+ Python (Flask/Django)
+ Angular 2+
+ Machine learning and text analytics
+ NLP (spaCy, NLTK, Stanford CoreNLP, Gensim)
+ PyTorch, TensorFlow, Keras
+ Data visualization (Tableau, Pandas, D3, ggplot)
+ Redis/ElastiCache
+ MongoDB, DynamoDB, MySQL, PostgreSQL
+ OCR/image detection
+ Open-source PDF processing libraries