diff --git a/adapters/pubmatic/pubmatic.go b/adapters/pubmatic/pubmatic.go
index 8084b2bcabe..40a80a4eaa9 100644
--- a/adapters/pubmatic/pubmatic.go
+++ b/adapters/pubmatic/pubmatic.go
@@ -40,9 +40,14 @@ type pubmaticBidExtVideo struct {
 	Duration *int `json:"duration,omitempty"`
 }
 
+type pubmaticContext struct {
+	Data json.RawMessage `json:"data"`
+}
+
 type ExtImpBidderPubmatic struct {
 	adapters.ExtImpBidder
-	Data json.RawMessage `json:"data,omitempty"`
+	Data    json.RawMessage `json:"data,omitempty"`
+	Context pubmaticContext `json:"context"`
 }
 
 type ExtAdServer struct {
@@ -305,6 +310,10 @@ func parseImpressionObject(imp *openrtb2.Imp, extractWrapperExtFromImp, extractP
 		populateFirstPartyDataImpAttributes(bidderExt.Data, extMap)
 	}
 
+	if len(bidderExt.Context.Data) > 0 {
+		populateFirstPartyDataImpAttributes(bidderExt.Context.Data, extMap)
+	}
+
 	imp.Ext = nil
 	if len(extMap) > 0 {
 		ext, err := json.Marshal(extMap)
diff --git a/exchange/exchange.go b/exchange/exchange.go
index 24ca193f989..737091d4ba8 100644
--- a/exchange/exchange.go
+++ b/exchange/exchange.go
@@ -348,13 +348,12 @@ func (e *exchange) HoldAuction(ctx context.Context, r *AuctionRequest, debugLog
 		liveAdapters []openrtb_ext.BidderName
 	)
 
-	if len(r.StoredAuctionResponses) > 0 {
-		adapterBids, fledge, liveAdapters, err = buildStoredAuctionResponse(r.StoredAuctionResponses)
+	shouldMspBackfillBids := mspUpdateStoredAuctionResponse(r)
+	if len(r.StoredAuctionResponses) > 0 && !shouldMspBackfillBids {
+		adapterBids, fledge, liveAdapters, err, anyBidsReturned = mspApplyStoredAuctionResponse(r)
 		if err != nil {
 			return nil, err
 		}
-		anyBidsReturned = true
-
 	} else {
 		// List of bidders we have requests for.
 		liveAdapters = listBiddersWithRequests(bidderRequests)
@@ -367,6 +366,10 @@ func (e *exchange) HoldAuction(ctx context.Context, r *AuctionRequest, debugLog
 			alternateBidderCodes = *r.Account.AlternateBidderCodes
 		}
 		adapterBids, adapterExtra, fledge, anyBidsReturned = e.getAllBids(auctionCtx, bidderRequests, bidAdjustmentFactors, conversions, accountDebugAllow, r.GlobalPrivacyControlHeader, debugLog.DebugOverride, alternateBidderCodes, requestExtLegacy.Prebid.Experiment, r.HookExecutor, r.StartTime, bidAdjustmentRules)
+		adapterBids, fledge, liveAdapters, err, anyBidsReturned = mspPostProcessAuction(r, liveAdapters, adapterBids, adapterExtra, fledge, anyBidsReturned, shouldMspBackfillBids)
+		if err != nil {
+			return nil, err
+		}
 		r.MakeBidsTimeInfo = buildMakeBidsTimeInfoMap(adapterExtra)
 	}
 
diff --git a/exchange/msp_exchange.go b/exchange/msp_exchange.go
new file mode 100644
index 00000000000..9a712c382ca
--- /dev/null
+++ b/exchange/msp_exchange.go
@@ -0,0 +1,62 @@
+package exchange
+
+import (
+	"encoding/json"
+	"time"
+
+	"github.com/prebid/openrtb/v19/openrtb2"
+	"github.com/prebid/prebid-server/exchange/entities"
+	"github.com/prebid/prebid-server/openrtb_ext"
+)
+
+const (
+	MSP_SEAT_IN_HOUSE = "msp-in-house"
+)
+
+func mspUpdateStoredAuctionResponse(r *AuctionRequest) bool {
+	if len(r.StoredAuctionResponses) > 0 {
+		if rawSeatBid, ok := r.StoredAuctionResponses[r.BidRequestWrapper.Imp[0].ID]; ok {
+			var seatBids []openrtb2.SeatBid
+
+			err := json.Unmarshal(rawSeatBid, &seatBids)
+			if err == nil && len(seatBids) > 0 && seatBids[0].Seat == MSP_SEAT_IN_HOUSE {
+				// when price is the same, randomly choose one
+				swapIdx := time.Now().Second() % len(seatBids[0].Bid)
+				seatBids[0].Bid[0], seatBids[0].Bid[swapIdx] = seatBids[0].Bid[swapIdx], seatBids[0].Bid[0]
+				updatedJson, _ := json.Marshal(seatBids)
+				r.StoredAuctionResponses[r.BidRequestWrapper.Imp[0].ID] = updatedJson
+				return true
+			}
+		}
+	}
+
+	return false
+}
+
+func mspApplyStoredAuctionResponse(r *AuctionRequest) (map[openrtb_ext.BidderName]*entities.PbsOrtbSeatBid,
+	*openrtb_ext.Fledge,
+	[]openrtb_ext.BidderName,
+	error, bool) {
+	adapterBids, fledge, liveAdapters, err := buildStoredAuctionResponse(r.StoredAuctionResponses)
+	return adapterBids, fledge, liveAdapters, err, err == nil
+}
+
+func mspPostProcessAuction(
+	r *AuctionRequest,
+	liveAdapters []openrtb_ext.BidderName,
+	adapterBids map[openrtb_ext.BidderName]*entities.PbsOrtbSeatBid,
+	adapterExtra map[openrtb_ext.BidderName]*seatResponseExtra,
+	fledge *openrtb_ext.Fledge,
+	anyBidsReturned bool,
+	shouldMspBackfillBids bool) (map[openrtb_ext.BidderName]*entities.PbsOrtbSeatBid,
+	*openrtb_ext.Fledge,
+	[]openrtb_ext.BidderName,
+	error, bool) {
+	// TODO: freqcap, blocking
+
+	if shouldMspBackfillBids && !anyBidsReturned {
+		return mspApplyStoredAuctionResponse(r)
+	}
+
+	return adapterBids, fledge, liveAdapters, nil, anyBidsReturned
+}