diff --git a/pkg/client/client.go b/pkg/client/client.go
index b55b2bc..03115da 100644
--- a/pkg/client/client.go
+++ b/pkg/client/client.go
@@ -4,6 +4,7 @@ import (
 	"encoding/binary"
 	"fmt"
 	"net/http"
+	"sync"
 	"time"
 
 	"git.tijl.dev/tijl/shortify/pkg/generation"
@@ -19,6 +20,12 @@ type Client struct {
 	db         *bolt.DB
 	retryQueue chan shortenJob
 	stopRetry  chan struct{}
+
+	// In-memory cache
+	cacheMap     map[string]string // longURL -> shortID
+	cacheLock    sync.RWMutex
+	maxCacheSize int
+	cacheCount   int
 }
 
 // NewClient with persistence and retry queue
@@ -41,6 +48,10 @@ func NewClient(serverURL string, folder string) (*Client, error) {
 		stopRetry:  make(chan struct{}),
 	}
 
+	cli.cacheMap = make(map[string]string)
+	cli.maxCacheSize = 10000 // or make this configurable
+	cli.cacheCount = 0
+
 	// Create buckets if not exist
 	err = db.Update(func(tx *bolt.Tx) error {
 		_, err := tx.CreateBucketIfNotExists([]byte(bucketPrefix))
@@ -48,7 +59,16 @@ func NewClient(serverURL string, folder string) (*Client, error) {
 			return err
 		}
 		_, err = tx.CreateBucketIfNotExists([]byte(bucketRetryJobs))
-		return err
+		if err != nil {
+			return err
+		}
+
+		_, err = tx.CreateBucketIfNotExists([]byte(bucketURLCache))
+		if err != nil {
+			return err
+		}
+
+		return nil
 	})
 	if err != nil {
 		return nil, err
@@ -91,6 +111,20 @@ func NewClient(serverURL string, folder string) (*Client, error) {
 	cli.prefix = prefix
 	cli.gen = generation.NewGenerator(prefix)
 
+	// load cache
+	_ = cli.db.View(func(tx *bolt.Tx) error {
+		b := tx.Bucket([]byte("url_cache"))
+		if b == nil {
+			return nil
+		}
+		c := b.Cursor()
+		for k, v := c.First(); k != nil && cli.cacheCount < cli.maxCacheSize; k, v = c.Next() {
+			cli.cacheMap[string(k)] = string(v)
+			cli.cacheCount++
+		}
+		return nil
+	})
+
 	// Load retry jobs from DB into channel
 	go cli.loadRetryJobs()
 
@@ -100,14 +134,68 @@ func NewClient(serverURL string, folder string) (*Client, error) {
 	return cli, nil
 }
 
-// Shorten creates a short URL and sends it async to the central server
-func (c *Client) Shorten(longURL string) string {
+/*
+Shorten
+*/
+
+type ShortenOpt func(*shortenOptions)
+
+type shortenOptions struct {
+	useCache bool
+}
+
+func UseCache() ShortenOpt {
+	return func(opts *shortenOptions) {
+		opts.useCache = true
+	}
+}
+
+func (c *Client) Shorten(longURL string, opts ...ShortenOpt) string {
+	options := shortenOptions{}
+	for _, opt := range opts {
+		opt(&options)
+	}
+
+	// Check memory cache
+	if options.useCache {
+		c.cacheLock.RLock()
+		if shortID, ok := c.cacheMap[longURL]; ok {
+			c.cacheLock.RUnlock()
+			return shortID
+		}
+		c.cacheLock.RUnlock()
+	}
+
+	// Generate new ID
 	shortID := c.gen.NextID()
 
+	// Queue job
 	go c.enqueueJob(shortenJob{
 		ID:  shortID,
 		URL: longURL,
 	})
 
+	// Async store in cache
+	if options.useCache {
+		go c.addToCache(longURL, shortID)
+	}
+
 	return shortID
 }
+
+func (c *Client) addToCache(longURL, shortID string) {
+	c.cacheLock.Lock()
+	if _, exists := c.cacheMap[longURL]; !exists && c.cacheCount < c.maxCacheSize {
+		c.cacheMap[longURL] = shortID
+		c.cacheCount++
+	}
+	c.cacheLock.Unlock()
+
+	// Async write to BoltDB
+	go func() {
+		_ = c.db.Update(func(tx *bolt.Tx) error {
+			b := tx.Bucket([]byte("url_cache"))
+			return b.Put([]byte(longURL), []byte(shortID))
+		})
+	}()
+}
diff --git a/pkg/client/store.go b/pkg/client/store.go
index df1d700..ac35e10 100644
--- a/pkg/client/store.go
+++ b/pkg/client/store.go
@@ -16,6 +16,7 @@ import (
 const (
 	bucketPrefix    = "prefix"
 	bucketRetryJobs = "retry_queue"
+	bucketURLCache  = "url_cache"
 	dbFileName      = "shorty_client.db"
 )