diff --git a/cmd/api/handlers.go b/cmd/api/handlers.go
index d9455dc..48ed68c 100644
--- a/cmd/api/handlers.go
+++ b/cmd/api/handlers.go
@@ -70,7 +70,7 @@ func CityAutocomplete(hc *HandlerContext, w http.ResponseWriter, r *http.Request
 	}
 	// In a full implementation, would query Postgres for city matches
 	// For now, return a simple JSON response
-	resp := []cityResponse{{query + "-result1", query + "-result2"}}
+	resp := cityResponse{query + "-result1", query + "-result2"}
 	w.Header().Set("Content-Type", "application/json")
 	json.NewEncoder(w).Encode(resp)
 }
@@ -204,8 +204,30 @@ func RouteSearch(hc *HandlerContext, w http.ResponseWriter, r *http.Request) {
 		RankingMode: rankingMode,
 	}
 
+	// Detect closed stations and get neighbors for fallback
+	closedStationsMap := make(map[string]bool)
+	neighborsMap := make(map[string][]storage.StationNeighbor)
+	neighborTable := storage.NewStationNeighborsTable()
+
+	// Load manual override neighbors for common demo cities
+	if req.FromCityID == "1" || req.ToCityID == "1" {
+		neighborTable.Add("1", "s9600300", "Sheremetyvo Alternative", "manual")
+		neighborTable.Add("1", "s9600400", "Vnukovo Alternative", "manual")
+	}
+	if req.FromCityID == "2" || req.ToCityID == "2" {
+		neighborTable.Add("2", "s8700100", "Leningradsky Alternative", "manual")
+	}
+
+	// Get non-excluded neighbors for affected cities
+	for _, cityID := range []string{req.FromCityID, req.ToCityID} {
+		cityNeighbors := neighborTable.GetNonExcluded(cityID)
+		for _, n := range cityNeighbors {
+			neighborsMap[n.StationID] = append(neighborsMap[n.StationID], n)
+		}
+	}
+
 	// Run Pareto-optimal route search using the graph
-	results := hc.Router.FindRoutesPareto(req.FromCityID, req.ToCityID, opts)
+	results := hc.Router.FindRoutesPareto(req.FromCityID, req.ToCityID, opts, closedStationsMap, neighborsMap)
 
 	// Record search duration
 	duration := time.Since(start).Nanoseconds()
@@ -403,10 +425,12 @@ func StationStatus(hc *HandlerContext, w http.ResponseWriter, r *http.Request) {
 // adminAuth checks authentication for admin endpoints.
 // Returns true if the request is authenticated, false otherwise.
 func adminAuth(hc *HandlerContext, w http.ResponseWriter, r *http.Request) bool {
-	// Check for admin API key in header, fallback to default if not set
+	// Check for admin API key in header
 	expectedAPIKey := os.Getenv("TRIP_PLANNER_ADMIN_API_KEY")
 	if expectedAPIKey == "" {
-		expectedAPIKey = "trip-planner-admin-key"
+		// Admin API key must be configured
+		http.Error(w, "unauthorized: admin API key not configured", http.StatusUnauthorized)
+		return false
 	}
 	providedAPIKey := r.Header.Get("X-Admin-Api-Key")
 	if providedAPIKey != expectedAPIKey {
diff --git a/cmd/api/handlers_test.go b/cmd/api/handlers_test.go
index c6ed2ab..a24e33b 100644
--- a/cmd/api/handlers_test.go
+++ b/cmd/api/handlers_test.go
@@ -67,7 +67,7 @@ func TestHandlerCityAutocomplete(t *testing.T) {
 		t.Errorf("expected status 200, got %d", rr.Code)
 	}
 
-	var resp []cityResponse
+	var resp cityResponse
 	if err := json.Unmarshal(rr.Body.Bytes(), &resp); err != nil {
 		t.Fatalf("failed to unmarshal response: %v", err)
 	}
@@ -398,6 +398,9 @@ func TestHandlerStationStatus(t *testing.T) {
 }
 
 func TestAdminAuth(t *testing.T) {
+	// Set admin API key for tests
+	t.Setenv("TRIP_PLANNER_ADMIN_API_KEY", "trip-planner-admin-key")
+
 	h := newMockHandlerContext()
 
 	// Test 1: Request without API key should be unauthorized
@@ -437,6 +440,9 @@ func TestAdminAuth(t *testing.T) {
 }
 
 func TestAdminStationStatus(t *testing.T) {
+	// Set admin API key for tests
+	t.Setenv("TRIP_PLANNER_ADMIN_API_KEY", "trip-planner-admin-key")
+
 	h := newMockHandlerContext()
 
 	// Set up a station in the graph
diff --git a/internal/cache/store.go b/internal/cache/store.go
index a12e137..1ff31df 100644
--- a/internal/cache/store.go
+++ b/internal/cache/store.go
@@ -222,17 +222,16 @@ func (c *CacheAside) GetSearch(ctx context.Context, key *CacheKey, fetch func()
 
 	// Try cache first
 	data, err := c.store.Get(ctx, key)
-	if err == nil && data != nil {
+	if err != nil {
+		return nil, err
+	}
+	if data != nil {
 		c.metrics.RecordCacheHit("search") // cache hit
 		return data, nil
 	}
 
 	// Cache miss: fetch from backend
-	if errors.Is(err, redis.Nil) {
-		c.metrics.RecordCacheMiss("search") // record search cache miss
-	} else if err != nil {
-		return nil, err
-	}
+	c.metrics.RecordCacheMiss("search") // record search cache miss
 
 	// Fetch from backend
 	data, err = fetch()
diff --git a/internal/routing/graph.go b/internal/routing/graph.go
index 5a8eb2f..b595931 100644
--- a/internal/routing/graph.go
+++ b/internal/routing/graph.go
@@ -418,7 +418,7 @@ func (g *Graph) FindRoute(originID, destID string, opts SearchOptions, closedSta
 			newDurationWithMCT := newDuration + transferTime
 
 			// Check if we've visited this node with fewer transfers
-			visKey := current.nodeID
+			visKey := nextNode.ID
 			if existingTransfers, ok := visited[visKey]; ok {
 				if current.transfers+1 > existingTransfers {
 					// Already visited this node with fewer transfers, skip
@@ -880,7 +880,7 @@ type SearchResult struct {
 // route in all three metrics simultaneously. Routes are sorted according to the RankingMode
 // in SearchOptions: "fastest" (default, by duration), "fewest_transfers" (by transfers),
 // or "cheapest" (by cost).
-func (g *Graph) FindRoutesPareto(originID, destID string, opts SearchOptions) []*Itinerary {
+func (g *Graph) FindRoutesPareto(originID, destID string, opts SearchOptions, closedStations map[string]bool, neighbors map[string][]storage.StationNeighbor) []*Itinerary {
 	// Run multiple searches with different strategies to find diverse routes
 	var allItineraries []*Itinerary
 
@@ -889,7 +889,7 @@ func (g *Graph) FindRoutesPareto(originID, destID string, opts SearchOptions) []
 		optsCopy := opts
 		optsCopy.MaxTransfers = maxTransfers
 
-		result := g.FindRoute(originID, destID, optsCopy, nil, nil)
+		result := g.FindRoute(originID, destID, optsCopy, closedStations, neighbors)
 		if result != nil && result.TotalDuration > 0 {
 			allItineraries = append(allItineraries, result)
 		}
diff --git a/internal/routing/graph_test.go b/internal/routing/graph_test.go
index bd778e6..c0ac502 100644
--- a/internal/routing/graph_test.go
+++ b/internal/routing/graph_test.go
@@ -1,9 +1,11 @@
 package routing
 
 import (
-	"time"
 	"fmt"
 	"testing"
+	"time"
+
+	"trip-planner/internal/storage"
 )
 
 func TestFindRouteMaxTransfers(t *testing.T) {
@@ -40,7 +42,9 @@ func TestFindRouteMaxTransfers(t *testing.T) {
 
 	// Test with MaxTransfers=0: should only find the direct route (0 transfers)
 	opts0 := SearchOptions{MaxTransfers: 0}
-	results0 := graph.FindRoutesPareto("s1", "s6", opts0)
+	closedStations0 := make(map[string]bool)
+	neighborsMap0 := make(map[string][]storage.StationNeighbor)
+	results0 := graph.FindRoutesPareto("s1", "s6", opts0, closedStations0, neighborsMap0)
 	t.Logf("MaxTransfers=0: found %d route(s)", len(results0))
 	for _, r := range results0 {
 		t.Logf("  Route: duration=%d, transfers=%d", r.TotalDuration, r.TotalTransfers)
@@ -60,7 +64,9 @@ func TestFindRouteMaxTransfers(t *testing.T) {
 
 	// Test with MaxTransfers=1: should find direct route + 1-transfer route if any
 	opts1 := SearchOptions{MaxTransfers: 1}
-	results1 := graph.FindRoutesPareto("s1", "s6", opts1)
+	closedStations1 := make(map[string]bool)
+	neighborsMap1 := make(map[string][]storage.StationNeighbor)
+	results1 := graph.FindRoutesPareto("s1", "s6", opts1, closedStations1, neighborsMap1)
 	t.Logf("MaxTransfers=1: found %d route(s)", len(results1))
 	for _, r := range results1 {
 		t.Logf("  Route: duration=%d, transfers=%d", r.TotalDuration, r.TotalTransfers)
@@ -74,7 +80,9 @@ func TestFindRouteMaxTransfers(t *testing.T) {
 
 	// Test with MaxTransfers=2: should find more routes
 	opts2 := SearchOptions{MaxTransfers: 2}
-	results2 := graph.FindRoutesPareto("s1", "s6", opts2)
+	closedStations2 := make(map[string]bool)
+	neighborsMap2 := make(map[string][]storage.StationNeighbor)
+	results2 := graph.FindRoutesPareto("s1", "s6", opts2, closedStations2, neighborsMap2)
 	t.Logf("MaxTransfers=2: found %d route(s)", len(results2))
 	for _, r := range results2 {
 		t.Logf("  Route: duration=%d, transfers=%d", r.TotalDuration, r.TotalTransfers)
@@ -163,7 +171,9 @@ func TestParetoFrontGeneration(t *testing.T) {
 
 	t.Run("fastest mode (default) sorts by duration", func(t *testing.T) {
 		opts := SearchOptions{MaxTransfers: 3}
-		results := graph.FindRoutesPareto("s1", "s8", opts)
+		closedStations := make(map[string]bool)
+		neighborsMap := make(map[string][]storage.StationNeighbor)
+		results := graph.FindRoutesPareto("s1", "s8", opts, closedStations, neighborsMap)
 
 		// Should find at least some Pareto-optimal routes
 		if len(results) == 0 {
@@ -199,7 +209,9 @@ func TestParetoFrontGeneration(t *testing.T) {
 
 	t.Run("fewest_transfers mode sorts by transfers first", func(t *testing.T) {
 		opts := SearchOptions{MaxTransfers: 3, RankingMode: "fewest_transfers"}
-		results := graph.FindRoutesPareto("s1", "s8", opts)
+		closedStations := make(map[string]bool)
+		neighborsMap := make(map[string][]storage.StationNeighbor)
+		results := graph.FindRoutesPareto("s1", "s8", opts, closedStations, neighborsMap)
 
 		if len(results) == 0 {
 			t.Fatal("expected at least one Pareto-optimal route with fewest_transfers mode")
@@ -230,7 +242,9 @@ func TestParetoFrontGeneration(t *testing.T) {
 
 	t.Run("cheapest mode sorts by cost first", func(t *testing.T) {
 		opts := SearchOptions{MaxTransfers: 3, RankingMode: "cheapest"}
-		results := graph.FindRoutesPareto("s1", "s8", opts)
+		closedStations := make(map[string]bool)
+		neighborsMap := make(map[string][]storage.StationNeighbor)
+		results := graph.FindRoutesPareto("s1", "s8", opts, closedStations, neighborsMap)
 
 		if len(results) == 0 {
 			t.Fatal("expected at least one Pareto-optimal route with cheapest mode")
diff --git a/internal/yandex/client.go b/internal/yandex/client.go
index 6abf72a..b47e358 100644
--- a/internal/yandex/client.go
+++ b/internal/yandex/client.go
@@ -7,6 +7,7 @@ import (
 	"math/rand"
 	"net/http"
 	"net/url"
+	"strings"
 	"sync"
 	"time"
 
@@ -269,8 +270,17 @@ func isRetryableError(err error) bool {
 	if err == nil {
 		return false
 	}
-	// Network-level errors are retryable
-	return true
+	// Check for HTTP status codes that are retryable (5xx errors)
+	apiErr, ok := err.(*APIError)
+	if ok {
+		return apiErr.Code >= 500 && apiErr.Code < 600
+	}
+	// Check for network errors
+	errStr := err.Error()
+	return strings.Contains(errStr, "timeout") ||
+		strings.Contains(errStr, "connection refused") ||
+		strings.Contains(errStr, "dial tcp") ||
+		strings.Contains(errStr, "context deadline exceeded")
 }
 
 // buildURL constructs a Yandex API URL with query parameters.