diff --git a/chain/index/msgindex.go b/chain/index/msgindex.go
index accaf5fc9..ff5ddbdd9 100644
--- a/chain/index/msgindex.go
+++ b/chain/index/msgindex.go
@@ -7,6 +7,7 @@ import (
 	"io/fs"
 	"os"
 	"path"
+	"sync"
 	"time"
 
 	logging "github.com/ipfs/go-log/v2"
@@ -19,24 +20,6 @@ import (
 	"github.com/ipfs/go-cid"
 )
 
-// chain store interface; we could use store.ChainStore directly,
-// but this simplifies unit testing.
-type ChainStore interface {
-	SubscribeHeadChanges(f store.ReorgNotifee)
-}
-
-var _ ChainStore = (*store.ChainStore)(nil)
-
-type msgIndex struct {
-	cs ChainStore
-
-	db               *sql.DB
-	selectMsgStmt    *sql.Stmt
-	deleteTipSetStmt *sql.Stmt
-}
-
-var _ MsgIndex = (*msgIndex)(nil)
-
 var log = logging.Logger("msgindex")
 
 var (
@@ -47,6 +30,37 @@ var (
 	coalesceMergeInterval = 100 * time.Millisecond
 )
 
+// chain store interface; we could use store.ChainStore directly,
+// but this simplifies unit testing.
+type ChainStore interface {
+	SubscribeHeadChanges(f store.ReorgNotifee)
+	MessagesForBlock(ctx context.Context, b *types.BlockHeader) ([]*types.Message, []*types.SignedMessage, error)
+}
+
+var _ ChainStore = (*store.ChainStore)(nil)
+
+type msgIndex struct {
+	cs ChainStore
+
+	db               *sql.DB
+	selectMsgStmt    *sql.Stmt
+	insertMsgStmt    *sql.Stmt
+	deleteTipSetStmt *sql.Stmt
+
+	sema chan struct{}
+	mx   sync.Mutex
+	pend []headChange
+
+	cancel func()
+}
+
+var _ MsgIndex = (*msgIndex)(nil)
+
+type headChange struct {
+	rev []*types.TipSet
+	app []*types.TipSet
+}
+
 func NewMsgIndex(basePath string, cs ChainStore) (MsgIndex, error) {
 	var (
 		mkdb   bool
@@ -96,7 +110,15 @@ opendb:
 		}
 	}
 
-	msgIndex := &msgIndex{db: db, cs: cs}
+	ctx, cancel := context.WithCancel(context.Background())
+
+	msgIndex := &msgIndex{
+		db:     db,
+		cs:     cs,
+		sema:   make(chan struct{}, 1),
+		cancel: cancel,
+	}
+
 	err = msgIndex.prepareStatements()
 	if err != nil {
 		err2 := db.Close()
@@ -115,6 +137,8 @@ opendb:
 	)
 	cs.SubscribeHeadChanges(rnf)
 
+	go msgIndex.background(ctx)
+
 	return msgIndex, nil
 }
 
@@ -141,6 +165,12 @@ func (x *msgIndex) prepareStatements() error {
 	}
 	x.selectMsgStmt = stmt
 
+	stmt, err = x.db.Prepare("INSERT INTO Messages VALUES (?, ?, ?, ?)")
+	if err != nil {
+		return err
+	}
+	x.insertMsgStmt = stmt
+
 	stmt, err = x.db.Prepare("DELETE FROM Messages WHERE tipset = ?")
 	if err != nil {
 		return err
@@ -153,8 +183,124 @@ func (x *msgIndex) prepareStatements() error {
 
 // head change notifee
 func (x *msgIndex) onHeadChange(rev, app []*types.TipSet) error {
-	// TODO
-	return errors.New("TODO: msgIndex.onHeadChange")
+	// do it in the background to avoid blocking head change processing
+	x.mx.Lock()
+	x.pend = append(x.pend, headChange{rev: rev, app: app})
+	// TODO log loudly if this is building backlog (it shouldn't but better be safe on this)
+	x.mx.Unlock()
+
+	select {
+	case x.sema <- struct{}{}:
+	default:
+	}
+
+	return nil
+}
+
+func (x *msgIndex) background(ctx context.Context) {
+	for {
+		select {
+		case <-x.sema:
+			err := x.processHeadChanges(ctx)
+			if err != nil {
+				// TODO should we shut down the index altogether? we just log for now.
+				log.Errorf("error processing head change notifications: %s", err)
+			}
+
+		case <-ctx.Done():
+			return
+		}
+	}
+}
+
+func (x *msgIndex) processHeadChanges(ctx context.Context) error {
+	x.mx.Lock()
+	pend := x.pend
+	x.pend = nil
+	x.mx.Unlock()
+
+	txn, err := x.db.Begin()
+	if err != nil {
+		return xerrors.Errorf("error creating transaction: %w", err)
+	}
+
+	for _, hc := range pend {
+		for _, ts := range hc.rev {
+			if err := x.doRevert(ctx, ts); err != nil {
+				txn.Rollback()
+				return xerrors.Errorf("error reverting %s: %w", ts, err)
+			}
+		}
+
+		for _, ts := range hc.app {
+			if err := x.doApply(ctx, ts); err != nil {
+				txn.Rollback()
+				return xerrors.Errorf("error applying %s: %w", ts, err)
+			}
+		}
+	}
+
+	return txn.Commit()
+}
+
+func (x *msgIndex) doRevert(ctx context.Context, ts *types.TipSet) error {
+	tskey, err := ts.Key().Cid()
+	if err != nil {
+		return xerrors.Errorf("error computing tipset cid: %w", err)
+	}
+
+	key := tskey.String()
+	_, err = x.deleteTipSetStmt.Exec(key)
+	return err
+}
+
+func (x *msgIndex) doApply(ctx context.Context, ts *types.TipSet) error {
+	tscid, err := ts.Key().Cid()
+	if err != nil {
+		return xerrors.Errorf("error computing tipset cid: %w", err)
+	}
+
+	tskey := tscid.String()
+	xepoch := int64(ts.Height())
+	var xindex int64
+
+	seen := make(map[string]struct{})
+	insert := func(key string) error {
+		if _, ok := seen[key]; ok {
+			return nil
+		}
+
+		if _, err := x.insertMsgStmt.Exec(key, tskey, xepoch, xindex); err != nil {
+			return err
+		}
+		seen[key] = struct{}{}
+		xindex++
+
+		return nil
+	}
+
+	for _, blk := range ts.Blocks() {
+		bmsgs, smsgs, err := x.cs.MessagesForBlock(ctx, blk)
+		if err != nil {
+			return xerrors.Errorf("error retrieving messages for block %s in %s: %w", blk, ts, err)
+		}
+
+		for _, m := range bmsgs {
+			key := m.Cid().String()
+			if err := insert(key); err != nil {
+				return err
+			}
+		}
+
+		for _, m := range smsgs {
+			key := m.Cid().String()
+			if err := insert(key); err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
 }
 
 // interface