diff --git a/cmd/prometheus/main.go b/cmd/prometheus/main.go
index 9a940ab5d..d824668ed 100644
--- a/cmd/prometheus/main.go
+++ b/cmd/prometheus/main.go
@@ -96,6 +96,7 @@ func main() {
 		webTimeout          model.Duration
 		queryTimeout        model.Duration
 		queryConcurrency    int
+		queryMaxSamples     int
 		RemoteFlushDeadline model.Duration
 
 		prometheusURL string
@@ -197,6 +198,8 @@ func main() {
 
 	a.Flag("query.max-concurrency", "Maximum number of queries executed concurrently.").
 		Default("20").IntVar(&cfg.queryConcurrency)
+	a.Flag("query.max-samples", "Maximum number of samples a single query can load into memory. Note that queries will fail if they would load more samples than this into memory, so this also limits the number of samples a query can return.").
+		Default("50000000").IntVar(&cfg.queryMaxSamples)
 
 	promlogflag.AddFlags(a, &cfg.logLevel)
 
@@ -264,12 +267,14 @@ func main() {
 
 		scrapeManager = scrape.NewManager(log.With(logger, "component", "scrape manager"), fanoutStorage)
 
-		queryEngine = promql.NewEngine(
-			log.With(logger, "component", "query engine"),
-			prometheus.DefaultRegisterer,
-			cfg.queryConcurrency,
-			time.Duration(cfg.queryTimeout),
-		)
+		opts = promql.EngineOpts{
+			Logger:        log.With(logger, "component", "query engine"),
+			Reg:           prometheus.DefaultRegisterer,
+			MaxConcurrent: cfg.queryConcurrency,
+			MaxSamples:    cfg.queryMaxSamples,
+			Timeout:       time.Duration(cfg.queryTimeout),
+		}
+		queryEngine = promql.NewEngine(opts)
 
 		ruleManager = rules.NewManager(&rules.ManagerOptions{
 			Appendable:      fanoutStorage,
diff --git a/promql/bench_test.go b/promql/bench_test.go
index 4bdddb13e..fef667927 100644
--- a/promql/bench_test.go
+++ b/promql/bench_test.go
@@ -28,7 +28,14 @@ import (
 func BenchmarkRangeQuery(b *testing.B) {
 	storage := testutil.NewStorage(b)
 	defer storage.Close()
-	engine := NewEngine(nil, nil, 10, 100*time.Second)
+	opts := EngineOpts{
+		Logger:        nil,
+		Reg:           nil,
+		MaxConcurrent: 10,
+		MaxSamples:    10,
+		Timeout:       100 * time.Second,
+	}
+	engine := NewEngine(opts)
 
 	metrics := []labels.Labels{}
 	metrics = append(metrics, labels.FromStrings("__name__", "a_one"))
diff --git a/promql/engine.go b/promql/engine.go
index e8ca8b7eb..009862b7a 100644
--- a/promql/engine.go
+++ b/promql/engine.go
@@ -43,6 +43,7 @@ const (
 	namespace = "prometheus"
 	subsystem = "engine"
 	queryTag  = "query"
+	env       = "query execution"
 
 	// The largest SampleValue that can be converted to an int64 without overflow.
 	maxInt64 = 9223372036854774784
@@ -69,13 +70,22 @@ type (
 	ErrQueryTimeout string
 	// ErrQueryCanceled is returned if a query was canceled during processing.
 	ErrQueryCanceled string
+	// ErrTooManySamples is returned if a query would woud load more than the maximum allowed samples into memory.
+	ErrTooManySamples string
 	// ErrStorage is returned if an error was encountered in the storage layer
 	// during query handling.
 	ErrStorage error
 )
 
-func (e ErrQueryTimeout) Error() string  { return fmt.Sprintf("query timed out in %s", string(e)) }
-func (e ErrQueryCanceled) Error() string { return fmt.Sprintf("query was canceled in %s", string(e)) }
+func (e ErrQueryTimeout) Error() string {
+	return fmt.Sprintf("query timed out in %s", string(e))
+}
+func (e ErrQueryCanceled) Error() string {
+	return fmt.Sprintf("query was canceled in %s", string(e))
+}
+func (e ErrTooManySamples) Error() string {
+	return fmt.Sprintf("query processing would load too many samples into memory in %s", string(e))
+}
 
 // A Query is derived from an a raw query string and can be run against an engine
 // it is associated with.
@@ -166,19 +176,29 @@ func contextErr(err error, env string) error {
 	}
 }
 
+// EngineOpts contains configuration options used when creating a new Engine.
+type EngineOpts struct {
+	Logger        log.Logger
+	Reg           prometheus.Registerer
+	MaxConcurrent int
+	MaxSamples    int
+	Timeout       time.Duration
+}
+
 // Engine handles the lifetime of queries from beginning to end.
 // It is connected to a querier.
 type Engine struct {
-	logger  log.Logger
-	metrics *engineMetrics
-	timeout time.Duration
-	gate    *gate.Gate
+	logger             log.Logger
+	metrics            *engineMetrics
+	timeout            time.Duration
+	gate               *gate.Gate
+	maxSamplesPerQuery int
 }
 
 // NewEngine returns a new engine.
-func NewEngine(logger log.Logger, reg prometheus.Registerer, maxConcurrent int, timeout time.Duration) *Engine {
-	if logger == nil {
-		logger = log.NewNopLogger()
+func NewEngine(opts EngineOpts) *Engine {
+	if opts.Logger == nil {
+		opts.Logger = log.NewNopLogger()
 	}
 
 	metrics := &engineMetrics{
@@ -223,10 +243,10 @@ func NewEngine(logger log.Logger, reg prometheus.Registerer, maxConcurrent int,
 			ConstLabels: prometheus.Labels{"slice": "result_sort"},
 		}),
 	}
-	metrics.maxConcurrentQueries.Set(float64(maxConcurrent))
+	metrics.maxConcurrentQueries.Set(float64(opts.MaxConcurrent))
 
-	if reg != nil {
-		reg.MustRegister(
+	if opts.Reg != nil {
+		opts.Reg.MustRegister(
 			metrics.currentQueries,
 			metrics.maxConcurrentQueries,
 			metrics.queryQueueTime,
@@ -236,10 +256,11 @@ func NewEngine(logger log.Logger, reg prometheus.Registerer, maxConcurrent int,
 		)
 	}
 	return &Engine{
-		gate:    gate.New(maxConcurrent),
-		timeout: timeout,
-		logger:  logger,
-		metrics: metrics,
+		gate:               gate.New(opts.MaxConcurrent),
+		timeout:            opts.Timeout,
+		logger:             opts.Logger,
+		metrics:            metrics,
+		maxSamplesPerQuery: opts.MaxSamples,
 	}
 }
 
@@ -384,6 +405,7 @@ func (ng *Engine) execEvalStmt(ctx context.Context, query *query, s *EvalStmt) (
 			endTimestamp:   start,
 			interval:       1,
 			ctx:            ctx,
+			maxSamples:     ng.maxSamplesPerQuery,
 			logger:         ng.logger,
 		}
 		val, err := evaluator.Eval(s.Expr)
@@ -424,6 +446,7 @@ func (ng *Engine) execEvalStmt(ctx context.Context, query *query, s *EvalStmt) (
 		endTimestamp:   timeMilliseconds(s.End),
 		interval:       durationMilliseconds(s.Interval),
 		ctx:            ctx,
+		maxSamples:     ng.maxSamplesPerQuery,
 		logger:         ng.logger,
 	}
 	val, err := evaluator.Eval(s.Expr)
@@ -575,11 +598,12 @@ type evaluator struct {
 	ctx context.Context
 
 	startTimestamp int64 // Start time in milliseconds.
+	endTimestamp   int64 // End time in milliseconds.
+	interval       int64 // Interval in milliseconds.
 
-	endTimestamp int64 // End time in milliseconds.
-	interval     int64 // Interval in milliseconds.
-
-	logger log.Logger
+	maxSamples     int
+	currentSamples int
+	logger         log.Logger
 }
 
 // errorf causes a panic with the input formatted into an error.
@@ -673,15 +697,18 @@ func (enh *EvalNodeHelper) signatureFunc(on bool, names ...string) func(labels.L
 
 // rangeEval evaluates the given expressions, and then for each step calls
 // the given function with the values computed for each expression at that
-// step.  The return value is the combination into time series of  of all the
+// step.  The return value is the combination into time series of all the
 // function call results.
 func (ev *evaluator) rangeEval(f func([]Value, *EvalNodeHelper) Vector, exprs ...Expr) Matrix {
 	numSteps := int((ev.endTimestamp-ev.startTimestamp)/ev.interval) + 1
 	matrixes := make([]Matrix, len(exprs))
 	origMatrixes := make([]Matrix, len(exprs))
+	originalNumSamples := ev.currentSamples
+
 	for i, e := range exprs {
 		// Functions will take string arguments from the expressions, not the values.
 		if e != nil && e.Type() != ValueTypeString {
+			// ev.currentSamples will be updated to the correct value within the ev.eval call.
 			matrixes[i] = ev.eval(e).(Matrix)
 
 			// Keep a copy of the original point slices so that they
@@ -704,17 +731,25 @@ func (ev *evaluator) rangeEval(f func([]Value, *EvalNodeHelper) Vector, exprs ..
 	}
 	enh := &EvalNodeHelper{out: make(Vector, 0, biggestLen)}
 	seriess := make(map[uint64]Series, biggestLen) // Output series by series hash.
+	tempNumSamples := ev.currentSamples
 	for ts := ev.startTimestamp; ts <= ev.endTimestamp; ts += ev.interval {
+		// Reset number of samples in memory after each timestamp.
+		ev.currentSamples = tempNumSamples
 		// Gather input vectors for this timestamp.
 		for i := range exprs {
 			vectors[i] = vectors[i][:0]
 			for si, series := range matrixes[i] {
 				for _, point := range series.Points {
 					if point.T == ts {
-						vectors[i] = append(vectors[i], Sample{Metric: series.Metric, Point: point})
-						// Move input vectors forward so we don't have to re-scan the same
-						// past points at the next step.
-						matrixes[i][si].Points = series.Points[1:]
+						if ev.currentSamples < ev.maxSamples {
+							vectors[i] = append(vectors[i], Sample{Metric: series.Metric, Point: point})
+							// Move input vectors forward so we don't have to re-scan the same
+							// past points at the next step.
+							matrixes[i][si].Points = series.Points[1:]
+							ev.currentSamples++
+						} else {
+							ev.error(ErrTooManySamples(env))
+						}
 					}
 					break
 				}
@@ -728,6 +763,16 @@ func (ev *evaluator) rangeEval(f func([]Value, *EvalNodeHelper) Vector, exprs ..
 			ev.errorf("vector cannot contain metrics with the same labelset")
 		}
 		enh.out = result[:0] // Reuse result vector.
+
+		ev.currentSamples += len(result)
+		// When we reset currentSamples to tempNumSamples during the next iteration of the loop it also
+		// needs to include the samples from the result here, as they're still in memory.
+		tempNumSamples += len(result)
+
+		if ev.currentSamples > ev.maxSamples {
+			ev.error(ErrTooManySamples(env))
+		}
+
 		// If this could be an instant query, shortcut so as not to change sort order.
 		if ev.endTimestamp == ev.startTimestamp {
 			mat := make(Matrix, len(result))
@@ -735,8 +780,10 @@ func (ev *evaluator) rangeEval(f func([]Value, *EvalNodeHelper) Vector, exprs ..
 				s.Point.T = ts
 				mat[i] = Series{Metric: s.Metric, Points: []Point{s.Point}}
 			}
+			ev.currentSamples = originalNumSamples + mat.TotalSamples()
 			return mat
 		}
+
 		// Add samples in output vector to output series.
 		for _, sample := range result {
 			h := sample.Metric.Hash()
@@ -750,19 +797,22 @@ func (ev *evaluator) rangeEval(f func([]Value, *EvalNodeHelper) Vector, exprs ..
 			sample.Point.T = ts
 			ss.Points = append(ss.Points, sample.Point)
 			seriess[h] = ss
+
 		}
 	}
+
 	// Reuse the original point slices.
 	for _, m := range origMatrixes {
 		for _, s := range m {
 			putPointSlice(s.Points)
 		}
 	}
-	// Assemble the output matrix.
+	// Assemble the output matrix. By the time we get here we know we don't have too many samples.
 	mat := make(Matrix, 0, len(seriess))
 	for _, ss := range seriess {
 		mat = append(mat, ss)
 	}
+	ev.currentSamples = originalNumSamples + mat.TotalSamples()
 	return mat
 }
 
@@ -802,6 +852,7 @@ func (ev *evaluator) eval(expr Expr) Value {
 				})
 			}
 		}
+
 		// Check if the function has a matrix argument.
 		var matrixArgIndex int
 		var matrixArg bool
@@ -887,7 +938,12 @@ func (ev *evaluator) eval(expr Expr) Value {
 				it.ReduceDelta(stepRange)
 			}
 			if len(ss.Points) > 0 {
-				mat = append(mat, ss)
+				if ev.currentSamples < ev.maxSamples {
+					mat = append(mat, ss)
+					ev.currentSamples += len(ss.Points)
+				} else {
+					ev.error(ErrTooManySamples(env))
+				}
 			}
 		}
 		if mat.ContainsSameLabelset() {
@@ -971,13 +1027,19 @@ func (ev *evaluator) eval(expr Expr) Value {
 			for ts := ev.startTimestamp; ts <= ev.endTimestamp; ts += ev.interval {
 				_, v, ok := ev.vectorSelectorSingle(it, e, ts)
 				if ok {
-					ss.Points = append(ss.Points, Point{V: v, T: ts})
+					if ev.currentSamples < ev.maxSamples {
+						ss.Points = append(ss.Points, Point{V: v, T: ts})
+						ev.currentSamples++
+					} else {
+						ev.error(ErrTooManySamples(env))
+					}
 				}
 			}
 
 			if len(ss.Points) > 0 {
 				mat = append(mat, ss)
 			}
+
 		}
 		return mat
 
@@ -1007,8 +1069,12 @@ func (ev *evaluator) vectorSelector(node *VectorSelector, ts int64) Vector {
 				Metric: node.series[i].Labels(),
 				Point:  Point{V: v, T: t},
 			})
+			ev.currentSamples++
 		}
 
+		if ev.currentSamples >= ev.maxSamples {
+			ev.error(ErrTooManySamples(env))
+		}
 	}
 	return vec
 }
@@ -1063,11 +1129,12 @@ func (ev *evaluator) matrixSelector(node *MatrixSelector) Matrix {
 		maxt   = ev.startTimestamp - offset
 		mint   = maxt - durationMilliseconds(node.Range)
 		matrix = make(Matrix, 0, len(node.series))
+		err    error
 	)
 
 	it := storage.NewBuffer(durationMilliseconds(node.Range))
 	for i, s := range node.series {
-		if err := contextDone(ev.ctx, "expression evaluation"); err != nil {
+		if err = contextDone(ev.ctx, "expression evaluation"); err != nil {
 			ev.error(err)
 		}
 		it.Reset(s.Iterator())
@@ -1127,14 +1194,22 @@ func (ev *evaluator) matrixIterSlice(it *storage.BufferedSeriesIterator, mint, m
 		}
 		// Values in the buffer are guaranteed to be smaller than maxt.
 		if t >= mint {
+			if ev.currentSamples >= ev.maxSamples {
+				ev.error(ErrTooManySamples(env))
+			}
 			out = append(out, Point{T: t, V: v})
+			ev.currentSamples++
 		}
 	}
 	// The seeked sample might also be in the range.
 	if ok {
 		t, v := it.Values()
 		if t == maxt && !value.IsStaleNaN(v) {
+			if ev.currentSamples >= ev.maxSamples {
+				ev.error(ErrTooManySamples(env))
+			}
 			out = append(out, Point{T: t, V: v})
+			ev.currentSamples++
 		}
 	}
 	return out
diff --git a/promql/engine_test.go b/promql/engine_test.go
index 6b9bf5665..adf99985d 100644
--- a/promql/engine_test.go
+++ b/promql/engine_test.go
@@ -27,9 +27,15 @@ import (
 )
 
 func TestQueryConcurrency(t *testing.T) {
-	concurrentQueries := 10
+	opts := EngineOpts{
+		Logger:        nil,
+		Reg:           nil,
+		MaxConcurrent: 10,
+		MaxSamples:    10,
+		Timeout:       100 * time.Second,
+	}
 
-	engine := NewEngine(nil, nil, concurrentQueries, 10*time.Second)
+	engine := NewEngine(opts)
 	ctx, cancelCtx := context.WithCancel(context.Background())
 	defer cancelCtx()
 
@@ -42,7 +48,7 @@ func TestQueryConcurrency(t *testing.T) {
 		return nil
 	}
 
-	for i := 0; i < concurrentQueries; i++ {
+	for i := 0; i < opts.MaxConcurrent; i++ {
 		q := engine.newTestQuery(f)
 		go q.Exec(ctx)
 		select {
@@ -74,13 +80,20 @@ func TestQueryConcurrency(t *testing.T) {
 	}
 
 	// Terminate remaining queries.
-	for i := 0; i < concurrentQueries; i++ {
+	for i := 0; i < opts.MaxConcurrent; i++ {
 		block <- struct{}{}
 	}
 }
 
 func TestQueryTimeout(t *testing.T) {
-	engine := NewEngine(nil, nil, 20, 5*time.Millisecond)
+	opts := EngineOpts{
+		Logger:        nil,
+		Reg:           nil,
+		MaxConcurrent: 20,
+		MaxSamples:    10,
+		Timeout:       5 * time.Millisecond,
+	}
+	engine := NewEngine(opts)
 	ctx, cancelCtx := context.WithCancel(context.Background())
 	defer cancelCtx()
 
@@ -99,7 +112,14 @@ func TestQueryTimeout(t *testing.T) {
 }
 
 func TestQueryCancel(t *testing.T) {
-	engine := NewEngine(nil, nil, 10, 10*time.Second)
+	opts := EngineOpts{
+		Logger:        nil,
+		Reg:           nil,
+		MaxConcurrent: 10,
+		MaxSamples:    10,
+		Timeout:       10 * time.Second,
+	}
+	engine := NewEngine(opts)
 	ctx, cancelCtx := context.WithCancel(context.Background())
 	defer cancelCtx()
 
@@ -165,7 +185,14 @@ func (errSeriesSet) At() storage.Series { return nil }
 func (e errSeriesSet) Err() error       { return e.err }
 
 func TestQueryError(t *testing.T) {
-	engine := NewEngine(nil, nil, 10, 10*time.Second)
+	opts := EngineOpts{
+		Logger:        nil,
+		Reg:           nil,
+		MaxConcurrent: 10,
+		MaxSamples:    10,
+		Timeout:       10 * time.Second,
+	}
+	engine := NewEngine(opts)
 	errStorage := ErrStorage(fmt.Errorf("storage error"))
 	queryable := storage.QueryableFunc(func(ctx context.Context, mint, maxt int64) (storage.Querier, error) {
 		return &errQuerier{err: errStorage}, nil
@@ -199,7 +226,14 @@ func TestQueryError(t *testing.T) {
 }
 
 func TestEngineShutdown(t *testing.T) {
-	engine := NewEngine(nil, nil, 10, 10*time.Second)
+	opts := EngineOpts{
+		Logger:        nil,
+		Reg:           nil,
+		MaxConcurrent: 10,
+		MaxSamples:    10,
+		Timeout:       10 * time.Second,
+	}
+	engine := NewEngine(opts)
 	ctx, cancelCtx := context.WithCancel(context.Background())
 
 	block := make(chan struct{})
@@ -360,6 +394,193 @@ load 10s
 
 }
 
+func TestMaxQuerySamples(t *testing.T) {
+	test, err := NewTest(t, `
+load 10s
+  metric 1 2
+`)
+
+	if err != nil {
+		t.Fatalf("unexpected error creating test: %q", err)
+	}
+	defer test.Close()
+
+	err = test.Run()
+	if err != nil {
+		t.Fatalf("unexpected error initializing test: %q", err)
+	}
+
+	cases := []struct {
+		Query      string
+		MaxSamples int
+		Result     Result
+		Start      time.Time
+		End        time.Time
+		Interval   time.Duration
+	}{
+		// Instant queries.
+		{
+			Query:      "1",
+			MaxSamples: 1,
+			Result: Result{
+				nil,
+				Scalar{V: 1, T: 1000}},
+			Start: time.Unix(1, 0),
+		},
+		{
+			Query:      "1",
+			MaxSamples: 0,
+			Result: Result{
+				ErrTooManySamples(env),
+				nil,
+			},
+			Start: time.Unix(1, 0),
+		},
+		{
+			Query:      "metric",
+			MaxSamples: 0,
+			Result: Result{
+				ErrTooManySamples(env),
+				nil,
+			},
+			Start: time.Unix(1, 0),
+		},
+		{
+			Query:      "metric",
+			MaxSamples: 1,
+			Result: Result{
+				nil,
+				Vector{
+					Sample{Point: Point{V: 1, T: 1000},
+						Metric: labels.FromStrings("__name__", "metric")},
+				},
+			},
+			Start: time.Unix(1, 0),
+		},
+		{
+			Query:      "metric[20s]",
+			MaxSamples: 2,
+			Result: Result{
+				nil,
+				Matrix{Series{
+					Points: []Point{{V: 1, T: 0}, {V: 2, T: 10000}},
+					Metric: labels.FromStrings("__name__", "metric")},
+				},
+			},
+			Start: time.Unix(10, 0),
+		},
+		{
+			Query:      "metric[20s]",
+			MaxSamples: 0,
+			Result: Result{
+				ErrTooManySamples(env),
+				nil,
+			},
+			Start: time.Unix(10, 0),
+		},
+		// Range queries.
+		{
+			Query:      "1",
+			MaxSamples: 3,
+			Result: Result{
+				nil,
+				Matrix{Series{
+					Points: []Point{{V: 1, T: 0}, {V: 1, T: 1000}, {V: 1, T: 2000}},
+					Metric: labels.FromStrings()},
+				},
+			},
+			Start:    time.Unix(0, 0),
+			End:      time.Unix(2, 0),
+			Interval: time.Second,
+		},
+		{
+			Query:      "1",
+			MaxSamples: 0,
+			Result: Result{
+				ErrTooManySamples(env),
+				nil,
+			},
+			Start:    time.Unix(0, 0),
+			End:      time.Unix(2, 0),
+			Interval: time.Second,
+		},
+		{
+			Query:      "metric",
+			MaxSamples: 3,
+			Result: Result{
+				nil,
+				Matrix{Series{
+					Points: []Point{{V: 1, T: 0}, {V: 1, T: 1000}, {V: 1, T: 2000}},
+					Metric: labels.FromStrings("__name__", "metric")},
+				},
+			},
+			Start:    time.Unix(0, 0),
+			End:      time.Unix(2, 0),
+			Interval: time.Second,
+		},
+		{
+			Query:      "metric",
+			MaxSamples: 2,
+			Result: Result{
+				ErrTooManySamples(env),
+				nil,
+			},
+			Start:    time.Unix(0, 0),
+			End:      time.Unix(2, 0),
+			Interval: time.Second,
+		},
+		{
+			Query:      "metric",
+			MaxSamples: 3,
+			Result: Result{
+				nil,
+				Matrix{Series{
+					Points: []Point{{V: 1, T: 0}, {V: 1, T: 5000}, {V: 2, T: 10000}},
+					Metric: labels.FromStrings("__name__", "metric")},
+				},
+			},
+			Start:    time.Unix(0, 0),
+			End:      time.Unix(10, 0),
+			Interval: 5 * time.Second,
+		},
+		{
+			Query:      "metric",
+			MaxSamples: 2,
+			Result: Result{
+				ErrTooManySamples(env),
+				nil,
+			},
+			Start:    time.Unix(0, 0),
+			End:      time.Unix(10, 0),
+			Interval: 5 * time.Second,
+		},
+	}
+
+	engine := test.QueryEngine()
+	for _, c := range cases {
+		var err error
+		var qry Query
+
+		engine.maxSamplesPerQuery = c.MaxSamples
+
+		if c.Interval == 0 {
+			qry, err = engine.NewInstantQuery(test.Queryable(), c.Query, c.Start)
+		} else {
+			qry, err = engine.NewRangeQuery(test.Queryable(), c.Query, c.Start, c.End, c.Interval)
+		}
+		if err != nil {
+			t.Fatalf("unexpected error creating query: %q", err)
+		}
+		res := qry.Exec(test.Context())
+		if res.Err != nil && res.Err != c.Result.Err {
+			t.Fatalf("unexpected error running query: %q, expected to get result: %q", res.Err, c.Result.Value)
+		}
+		if !reflect.DeepEqual(res.Value, c.Result.Value) {
+			t.Fatalf("unexpected result for query %q: got %q wanted %q", c.Query, res.Value.String(), c.Result.String())
+		}
+	}
+}
+
 func TestRecoverEvaluatorRuntime(t *testing.T) {
 	ev := &evaluator{logger: log.NewNopLogger()}
 
diff --git a/promql/functions_test.go b/promql/functions_test.go
index 19680eb7f..d7134b3d7 100644
--- a/promql/functions_test.go
+++ b/promql/functions_test.go
@@ -29,7 +29,14 @@ func TestDeriv(t *testing.T) {
 	// so we test it by hand.
 	storage := testutil.NewStorage(t)
 	defer storage.Close()
-	engine := NewEngine(nil, nil, 10, 10*time.Second)
+	opts := EngineOpts{
+		Logger:        nil,
+		Reg:           nil,
+		MaxConcurrent: 10,
+		MaxSamples:    10000,
+		Timeout:       10 * time.Second,
+	}
+	engine := NewEngine(opts)
 
 	a, err := storage.Appender()
 	testutil.Ok(t, err)
diff --git a/promql/test.go b/promql/test.go
index f903e86e2..e90966cc8 100644
--- a/promql/test.go
+++ b/promql/test.go
@@ -506,7 +506,15 @@ func (t *Test) clear() {
 	}
 	t.storage = testutil.NewStorage(t)
 
-	t.queryEngine = NewEngine(nil, nil, 20, 10*time.Second)
+	opts := EngineOpts{
+		Logger:        nil,
+		Reg:           nil,
+		MaxConcurrent: 20,
+		MaxSamples:    1000,
+		Timeout:       100 * time.Second,
+	}
+
+	t.queryEngine = NewEngine(opts)
 	t.context, t.cancelCtx = context.WithCancel(context.Background())
 }
 
diff --git a/promql/value.go b/promql/value.go
index a57703081..2063f22d7 100644
--- a/promql/value.go
+++ b/promql/value.go
@@ -171,6 +171,15 @@ func (m Matrix) String() string {
 	return strings.Join(strs, "\n")
 }
 
+// TotalSamples returns the total number of samples in the series within a matrix.
+func (m Matrix) TotalSamples() int {
+	numSamples := 0
+	for _, series := range m {
+		numSamples += len(series.Points)
+	}
+	return numSamples
+}
+
 func (m Matrix) Len() int           { return len(m) }
 func (m Matrix) Less(i, j int) bool { return labels.Compare(m[i].Metric, m[j].Metric) < 0 }
 func (m Matrix) Swap(i, j int)      { m[i], m[j] = m[j], m[i] }
diff --git a/rules/manager_test.go b/rules/manager_test.go
index 429fcbb05..60f25cc52 100644
--- a/rules/manager_test.go
+++ b/rules/manager_test.go
@@ -494,7 +494,14 @@ func TestForStateRestore(t *testing.T) {
 func TestStaleness(t *testing.T) {
 	storage := testutil.NewStorage(t)
 	defer storage.Close()
-	engine := promql.NewEngine(nil, nil, 10, 10*time.Second)
+	engineOpts := promql.EngineOpts{
+		Logger:        nil,
+		Reg:           nil,
+		MaxConcurrent: 10,
+		MaxSamples:    10,
+		Timeout:       10 * time.Second,
+	}
+	engine := promql.NewEngine(engineOpts)
 	opts := &ManagerOptions{
 		QueryFunc:  EngineQueryFunc(engine, storage),
 		Appendable: storage,
@@ -623,7 +630,14 @@ func TestUpdate(t *testing.T) {
 	}
 	storage := testutil.NewStorage(t)
 	defer storage.Close()
-	engine := promql.NewEngine(nil, nil, 10, 10*time.Second)
+	opts := promql.EngineOpts{
+		Logger:        nil,
+		Reg:           nil,
+		MaxConcurrent: 10,
+		MaxSamples:    10,
+		Timeout:       10 * time.Second,
+	}
+	engine := promql.NewEngine(opts)
 	ruleManager := NewManager(&ManagerOptions{
 		Appendable: storage,
 		TSDB:       storage,
@@ -655,7 +669,14 @@ func TestUpdate(t *testing.T) {
 func TestNotify(t *testing.T) {
 	storage := testutil.NewStorage(t)
 	defer storage.Close()
-	engine := promql.NewEngine(nil, nil, 10, 10*time.Second)
+	engineOpts := promql.EngineOpts{
+		Logger:        nil,
+		Reg:           nil,
+		MaxConcurrent: 10,
+		MaxSamples:    10,
+		Timeout:       10 * time.Second,
+	}
+	engine := promql.NewEngine(engineOpts)
 	var lastNotified []*Alert
 	notifyFunc := func(ctx context.Context, expr string, alerts ...*Alert) {
 		lastNotified = alerts
diff --git a/rules/recording_test.go b/rules/recording_test.go
index 484474140..97133f9e4 100644
--- a/rules/recording_test.go
+++ b/rules/recording_test.go
@@ -28,7 +28,15 @@ func TestRuleEval(t *testing.T) {
 	storage := testutil.NewStorage(t)
 	defer storage.Close()
 
-	engine := promql.NewEngine(nil, nil, 10, 10*time.Second)
+	opts := promql.EngineOpts{
+		Logger:        nil,
+		Reg:           nil,
+		MaxConcurrent: 10,
+		MaxSamples:    10,
+		Timeout:       10 * time.Second,
+	}
+
+	engine := promql.NewEngine(opts)
 	ctx, cancelCtx := context.WithCancel(context.Background())
 	defer cancelCtx()
 
diff --git a/web/api/v1/api_test.go b/web/api/v1/api_test.go
index a04fd5115..c5739ebb9 100644
--- a/web/api/v1/api_test.go
+++ b/web/api/v1/api_test.go
@@ -151,7 +151,15 @@ func (m rulesRetrieverMock) RuleGroups() []*rules.Group {
 	storage := testutil.NewStorage(m.testing)
 	defer storage.Close()
 
-	engine := promql.NewEngine(nil, nil, 10, 10*time.Second)
+	engineOpts := promql.EngineOpts{
+		Logger:        nil,
+		Reg:           nil,
+		MaxConcurrent: 10,
+		MaxSamples:    10,
+		Timeout:       100 * time.Second,
+	}
+
+	engine := promql.NewEngine(engineOpts)
 	opts := &rules.ManagerOptions{
 		QueryFunc:  rules.EngineQueryFunc(engine, storage),
 		Appendable: storage,