Programmers' Toolbox

Kafka
(different levels) Retry Queue and Dead Letter Queen

Redis
SETNX key value
LRU, LRU
- Sample 3 or 5 keys, maintain a larger pool of candidate keys (16)
Pipeline
- Queue in client side
Translation
- Multi, exec, abort
- queued in server side
- Continue to execute even some commands fail, no rollback
- Use Watch to implement CAS, fail the translation if the key changes
- pub/sub
- sorted sort(zset), 
- hyperloglog, PFADD, PFCOUNT

- service side lua script

OkHttp

WebSocket
- efficiency: persistent duplex, bidirection connection

Java - @ServerEndpoint
Socket.io

LevelDB/RocksDB

jq
jq '.pods[] | .name, .replication'
'.owner.name'
'.likes[0]'
.[] return all elements in the array