diff --git a/commons/com.b2international.commons/src/com/b2international/commons/exceptions/TooCostlyException.java b/commons/com.b2international.commons/src/com/b2international/commons/exceptions/TooCostlyException.java
new file mode 100644
index 00000000000..4c3d2446a55
--- /dev/null
+++ b/commons/com.b2international.commons/src/com/b2international/commons/exceptions/TooCostlyException.java
@@ -0,0 +1,30 @@
+/*
+ * Copyright 2023 B2i Healthcare Pte Ltd, http://b2i.sg
+ * 
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.b2international.commons.exceptions;
+
+/**
+ * @since 8.10
+ */
+public final class TooCostlyException extends BadRequestException {
+
+	private static final long serialVersionUID = 1L;
+	
+	public TooCostlyException(String developerMessage, Object...args) {
+		super("Request is too costly to execute. Alter your input parameters so that the system is able to process your request.");
+		withDeveloperMessage(developerMessage, args);
+	}
+
+}
diff --git a/core/com.b2international.snowowl.core/src/com/b2international/snowowl/core/request/ecl/EclEvaluationRequest.java b/core/com.b2international.snowowl.core/src/com/b2international/snowowl/core/request/ecl/EclEvaluationRequest.java
index 5865c14d7e4..ea7a6421c9f 100644
--- a/core/com.b2international.snowowl.core/src/com/b2international/snowowl/core/request/ecl/EclEvaluationRequest.java
+++ b/core/com.b2international.snowowl.core/src/com/b2international/snowowl/core/request/ecl/EclEvaluationRequest.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2022 B2i Healthcare Pte Ltd, http://b2i.sg
+ * Copyright 2022-2023 B2i Healthcare Pte Ltd, http://b2i.sg
  * 
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -35,6 +35,7 @@
 
 import com.b2international.commons.CompareUtils;
 import com.b2international.commons.exceptions.BadRequestException;
+import com.b2international.commons.exceptions.TooCostlyException;
 import com.b2international.index.query.*;
 import com.b2international.index.revision.RevisionSearcher;
 import com.b2international.snomed.ecl.Ecl;
@@ -100,7 +101,11 @@ public void setIgnoredSyntaxErrorCodes(Set<String> ignoredSyntaxErrorCodes) {
 	}
 	
 	protected final Promise<Expression> evaluate(C context, EObject expression) {
-		return dispatcher.invoke(context, expression);
+		try {
+			return dispatcher.invoke(context, expression);
+		} catch (StackOverflowError e) {
+			throw new TooCostlyException("ECL expression contains too many clauses and the server is unable to process it.");
+		}
 	}
 
 	protected Promise<Expression> eval(C context, EObject eObject) {
diff --git a/snomed/com.b2international.snowowl.snomed.datastore.tests/src/com/b2international/snowowl/snomed/core/ecl/SnomedEclEvaluationRequestTest.java b/snomed/com.b2international.snowowl.snomed.datastore.tests/src/com/b2international/snowowl/snomed/core/ecl/SnomedEclEvaluationRequestTest.java
index 73282436fc2..3bfd729ba91 100644
--- a/snomed/com.b2international.snowowl.snomed.datastore.tests/src/com/b2international/snowowl/snomed/core/ecl/SnomedEclEvaluationRequestTest.java
+++ b/snomed/com.b2international.snowowl.snomed.datastore.tests/src/com/b2international/snowowl/snomed/core/ecl/SnomedEclEvaluationRequestTest.java
@@ -41,6 +41,7 @@
 import org.junit.runners.Parameterized.Parameters;
 
 import com.b2international.commons.exceptions.BadRequestException;
+import com.b2international.commons.exceptions.TooCostlyException;
 import com.b2international.index.query.Expression;
 import com.b2international.index.query.Expressions;
 import com.b2international.index.query.MatchNone;
@@ -452,6 +453,19 @@ public void largeIdSetWithOrOperators() throws Exception {
 			.collect(Collectors.joining(" OR ")));
 	}
 
+	// XXX until we figure out how to process these effectively
+	@Test(expected = TooCostlyException.class)
+	public void largeEclOrOperatorOnly() throws Exception {
+		eval(IntStream.range(0, 10_000)
+			.mapToObj(i -> {
+				if (i % 10 == 0) {
+					return "<" + RandomSnomedIdentiferGenerator.generateConceptId();
+				} else {
+					return RandomSnomedIdentiferGenerator.generateConceptId();
+				}
+			})
+			.collect(Collectors.joining(" OR ")));
+	}
 	
 	@Test(expected = BadRequestException.class)
 	public void binaryOperatorAmbiguityOrAnd() throws Exception {