diff --git a/README.md b/README.md
index a40dd4d..37df3fd 100644
--- a/README.md
+++ b/README.md
@@ -4,6 +4,7 @@ An in-process, in-memory database for Go.
 
 ## TO DO
 
+* [ ] wal: delete old entries
 * [ ] wal: shipping_test: secondary too far behind
 * [ ] wal: writer_test: call RecvWAL twice
 * [ ] wal: writer_test double start / stop
diff --git a/wal/db-sql.go b/wal/db-sql.go
index d8c942c..712952c 100644
--- a/wal/db-sql.go
+++ b/wal/db-sql.go
@@ -9,6 +9,8 @@ CREATE TABLE IF NOT EXISTS wal(
   Store      INTEGER NOT NULL,
   Data       BLOB
 ) WITHOUT ROWID;
+
+CREATE INDEX IF NOT EXISTS wal_created_at_index ON wal(CreatedAt);
 `
 
 const sqlWALMaxSeqNum = `
@@ -28,3 +30,6 @@ FROM
 WHERE
   SeqNum > ?
 ORDER BY SeqNum ASC`
+
+const sqlWALDeleteQuery = `
+DELETE FROM wal WHERE CreatedAt < ? AND SeqNum < (SELECT MAX(SeqNum) FROM wal)`
diff --git a/wal/follower.go b/wal/follower.go
index 98ca580..5dffb44 100644
--- a/wal/follower.go
+++ b/wal/follower.go
@@ -66,14 +66,11 @@ func (f *Follower) SendWAL(conn net.Conn) {
 	defer conn.Close()
 
 	var (
-		buf               = make([]byte, 8)
-		headerBuf         = make([]byte, recHeaderSize)
-		empty             = make([]byte, recHeaderSize)
-		timeout           = 16 * time.Second
-		heartbeatInterval = time.Second * 2
-		pollInterval      = 200 * time.Millisecond
-		tStart            time.Time
-		err               error
+		buf       = make([]byte, 8)
+		headerBuf = make([]byte, recHeaderSize)
+		empty     = make([]byte, recHeaderSize)
+		tStart    time.Time
+		err       error
 	)
 
 	// Read the fromID from the conn.
@@ -87,7 +84,7 @@ func (f *Follower) SendWAL(conn net.Conn) {
 
 POLL:
 
-	conn.SetWriteDeadline(time.Now().Add(timeout))
+	conn.SetWriteDeadline(time.Now().Add(connTimeout))
 	tStart = time.Now()
 	for time.Since(tStart) < heartbeatInterval {
 		if f.MaxSeqNum() > afterSeqNum {
@@ -99,7 +96,7 @@ POLL:
 
 HEARTBEAT:
 
-	conn.SetWriteDeadline(time.Now().Add(timeout))
+	conn.SetWriteDeadline(time.Now().Add(connTimeout))
 	if _, err := conn.Write(empty); err != nil {
 		log.Printf("SendWAL failed to send heartbeat: %v", err)
 		return
@@ -110,7 +107,7 @@ HEARTBEAT:
 REPLAY:
 
 	err = f.Replay(afterSeqNum, func(rec Record) error {
-		conn.SetWriteDeadline(time.Now().Add(timeout))
+		conn.SetWriteDeadline(time.Now().Add(connTimeout))
 
 		afterSeqNum = rec.SeqNum
 		encodeRecordHeader(rec, headerBuf)
diff --git a/wal/global.go b/wal/global.go
new file mode 100644
index 0000000..74a28e1
--- /dev/null
+++ b/wal/global.go
@@ -0,0 +1,9 @@
+package wal
+
+import "time"
+
+var (
+	connTimeout       = 16 * time.Second       // For sending / receiving WAL.
+	heartbeatInterval = 2 * time.Second        // Used in Follower.SendLog
+	pollInterval      = 250 * time.Millisecond // Used in Follower.SendLog
+)
diff --git a/wal/shipping_test.go b/wal/shipping_test.go
index 6dbd3b0..5a6c301 100644
--- a/wal/shipping_test.go
+++ b/wal/shipping_test.go
@@ -74,7 +74,7 @@ func TestShipping(t *testing.T) {
 		defer nw.CloseClient()
 		defer nw.CloseServer()
 
-		N := 2000
+		N := 4000
 		sleepTime := time.Millisecond
 		go func() {
 			for i := 0; i < N; i++ {
@@ -138,7 +138,39 @@ func TestShipping(t *testing.T) {
 		}
 	})
 
-	run("TODO: secondary too far behind", func(t *testing.T, wWALPath, fWALPath string, w *Writer, nw *testconn.Network) {
+	run("secondary too far behind", func(t *testing.T, wWALPath, fWALPath string, w *Writer, nw *testconn.Network) {
+		// Write some entries to the primary.
+		// MaxSeqNum will be 10.
+		for i := 0; i < 10; i++ {
+			w.Store(randString(), randID(), _b(randString()))
+		}
+
+		// Delete everything.
+		w.DeleteBefore(time.Now().Unix() + 2)
+
+		// Run a sender in the background.
+		go func() {
+			f := NewFollower(wWALPath)
+			defer f.Close()
+			conn := nw.Accept()
+			f.SendWAL(conn)
+		}()
+
+		// Run the follower.
+		go func() {
+			w := NewWriterSecondary(fWALPath)
+			defer w.Close()
+			conn := nw.Dial()
+			w.RecvWAL(conn)
+		}()
+
+		time.Sleep(1)
+
+		f := NewFollower(fWALPath)
+		defer f.Close()
+		if f.MaxSeqNum() != 0 {
+			t.Fatal(f.MaxSeqNum())
+		}
 
 	})
 
diff --git a/wal/writer.go b/wal/writer.go
index 6a1ac2e..bb7a686 100644
--- a/wal/writer.go
+++ b/wal/writer.go
@@ -138,8 +138,6 @@ func (w *Writer) RecvWAL(conn net.Conn) {
 	}
 	defer w.recvLock.Unlock()
 
-	timeout := 16 * time.Second
-
 	headerBuf := make([]byte, recHeaderSize)
 	buf := make([]byte, 8)
 
@@ -147,7 +145,7 @@ func (w *Writer) RecvWAL(conn net.Conn) {
 	expectedSeqNum := afterSeqNum + 1
 
 	// Send fromID to the conn.
-	conn.SetWriteDeadline(time.Now().Add(timeout))
+	conn.SetWriteDeadline(time.Now().Add(connTimeout))
 	binary.LittleEndian.PutUint64(buf, afterSeqNum)
 	if _, err := conn.Write(buf); err != nil {
 		log.Printf("RecvWAL failed to send after sequence number: %v", err)
@@ -160,7 +158,7 @@ func (w *Writer) RecvWAL(conn net.Conn) {
 	defer w.stop()
 
 	for {
-		conn.SetReadDeadline(time.Now().Add(timeout))
+		conn.SetReadDeadline(time.Now().Add(connTimeout))
 		if _, err := conn.Read(headerBuf); err != nil {
 			log.Printf("RecvWAL failed to read header: %v", err)
 			return
@@ -205,3 +203,8 @@ func (w *Writer) RecvWAL(conn net.Conn) {
 		}
 	}
 }
+
+func (w *Writer) DeleteBefore(ts int64) {
+	_, err := w.db.Exec(sqlWALDeleteQuery, ts)
+	must(err)
+}