clockwork

this is clockwork: a Redis-compatible TCP key-value store written from scratch in Go.

it speaks RESP (Redis Serialization Protocol), so redis-cli and redis-benchmark work against it without modification. no Redis installed, no external dependencies, just the Go standard library.

Demo

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what it supports

• GET, SET with TTL flags (EX, PX, EXAT, PXAT)
• DEL, EXISTS
• INCR, DECR
• LPUSH, RPUSH, LRANGE
• SAVE — atomic persistence to disk via write-then-rename
• loads persisted state from dump.json on startup
• concurrent clients via goroutines, safe map access via sync.RWMutex

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run it

from source

git clone https://github.com/aryansaves/clockwork
cd clockwork
go run main.go

from docker

docker run -d -p 6379:6379 aryansaves/clockwork:latest

from release

download the latest binary for your platform from releases.

connect with redis-cli:

redis-cli -p 6379

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benchmark

100k requests, 50 concurrent clients against Clockwork and real Redis on the same machine.

Clockwork

Redis

Clockwork outperforms real Redis on raw GET/SET/INCR/LPUSH throughput. Real Redis carries overhead from its full feature surface — Clockwork doesn't. LRANGE degrades linearly with range size as expected.

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internals worth knowing

RESP parser — reads length-prefixed bulk strings off the TCP stream using bufio.Reader. skips $ lines (length headers), collects argument values directly.

typed store — values are stored as *RedisObject{Type, Value, TTL}. the interface{} value holds either string or []string depending on type. type mismatch returns WRONGTYPE error matching real Redis behavior.

lazy expiry — TTL is checked at read time, not by a background goroutine. expired keys are deleted on access. same approach real Redis uses for O(1) expiry without a sweeper.

list storage — lists are stored in reverse internal order so LPUSH is append() — O(1) amortized. LRANGE compensates with index inversion.

persistence — SAVE serializes the store to JSON, writes to a temp file, renames atomically. on startup, expired keys are discarded before loading.

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built against the codingchallenges.fyi Redis spec.