Fastime

Fastime is an ultra-fast time acquisition library for Go that returns the approximate current time with zero memory allocation, using a background goroutine to periodically update the cached time value.

Overview

In high-performance Go applications, calling time.Now() on every request can become a measurable cost — each call involves a system call that incurs kernel overhead. Fastime eliminates this by maintaining a cached time value that is updated by a background goroutine, providing nanosecond-level time retrieval with zero allocations.

Key Features

Zero allocation — allocs/op: 0 in the hot path
Background update — a dedicated goroutine refreshes the cached time at a configurable interval
Drop-in replacement — API-compatible with common time.Now() usage patterns
Configurable precision — trade off between freshness and performance by adjusting the update interval
Thread-safe — safe for concurrent access from any number of goroutines

Usage

import "github.com/kpango/fastime"

// Get current time (approximately)
now := fastime.Now()

// Get Unix timestamp
unix := fastime.UnixNanoNow()

// Format time
formatted := fastime.FormattedNow()

Design

Fastime spawns a single background goroutine that calls time.Now() at regular intervals and stores the result atomically. All reads from fastime.Now() simply load the cached value — no system call, no allocation. This makes it ideal for timestamping high-frequency events where nanosecond precision is not required.

Production Use

Fastime is widely adopted within LY Corporation's Go ecosystem for low-overhead time retrieval in performance-critical paths, including:

Vald — timestamping in the distributed vector search engine
Athenz products — token and certificate expiration checks
Ad delivery systems — high-frequency event logging and metrics