diff --git a/src/lib/probe-validator.ts b/src/lib/probe-validator.ts
index 40e6bd27..794f9c38 100644
--- a/src/lib/probe-validator.ts
+++ b/src/lib/probe-validator.ts
@@ -3,38 +3,39 @@ import TTLCache from '@isaacs/ttlcache';
 import { type RedisCluster, getMeasurementRedisClient } from './redis/measurement-client.js';
 
 export class ProbeValidator {
-	private readonly testIdToProbeId = new TTLCache<string, string>({
+	private readonly measurementIdToTests = new TTLCache<string, Map<string, string>>({
 		ttl: (config.get<number>('measurement.timeout') + 30) * 1000,
 	});
 
 	constructor (private readonly redis: RedisCluster) {}
 
 	addValidIds (measurementId: string, testId: string, probeUuid: string): void {
-		const key = ProbeValidator.getKey(measurementId, testId);
-		this.testIdToProbeId.set(key, probeUuid);
+		const measurement = this.measurementIdToTests.get(measurementId);
+
+		if (!measurement) {
+			this.measurementIdToTests.set(measurementId, new Map([ [ testId, probeUuid ] ]));
+		} else {
+			measurement.set(testId, probeUuid);
+		}
 	}
 
 	async validateProbe (measurementId: string, testId: string, probeUuid: string): Promise<void> {
-		const key = ProbeValidator.getKey(measurementId, testId);
-		let probeId = this.testIdToProbeId.get(key);
+		const measurement = this.measurementIdToTests.get(measurementId);
+		let probeId = measurement && measurement.get(testId);
 
 		if (!probeId) {
-			probeId = await this.getProbeIdFromRedis(key);
+			probeId = await this.getProbeIdFromRedis(measurementId, testId);
 		}
 
 		if (!probeId) {
-			throw new Error(`Probe ID not found for key ${key}`);
+			throw new Error(`Probe ID not found for measurement ID: ${measurementId}, test ID: ${testId}`);
 		} else if (probeId !== probeUuid) {
-			throw new Error(`Probe ID is wrong for key ${key}. Expected: ${probeId}, actual: ${probeUuid}`);
+			throw new Error(`Probe ID is wrong for measurement ID: ${measurementId}, test ID: ${testId}. Expected: ${probeId}, actual: ${probeUuid}`);
 		}
 	}
 
-	async getProbeIdFromRedis (key: string) {
-		return this.redis.hGet('gp:test-to-probe', key);
-	}
-
-	static getKey (measurementId: string, testId: string) {
-		return `${measurementId}_${testId}`;
+	async getProbeIdFromRedis (measurementId: string, testId: string) {
+		return this.redis.hGet('gp:test-to-probe', `${measurementId}_${testId}`);
 	}
 }
 
diff --git a/test/tests/unit/probe-validator.test.ts b/test/tests/unit/probe-validator.test.ts
index dd8f5ca7..e4b1c132 100644
--- a/test/tests/unit/probe-validator.test.ts
+++ b/test/tests/unit/probe-validator.test.ts
@@ -13,19 +13,21 @@ describe('ProbeValidator', () => {
 	});
 
 	it('should pass through valid probe id', async () => {
-		probeValidator.addValidIds('measurement-id', 'test-id', 'probe-uuid');
-		await probeValidator.validateProbe('measurement-id', 'test-id', 'probe-uuid');
+		probeValidator.addValidIds('measurement-id', 'test-id-0', 'probe-uuid-0');
+		probeValidator.addValidIds('measurement-id', 'test-id-1', 'probe-uuid-1');
+		await probeValidator.validateProbe('measurement-id', 'test-id-0', 'probe-uuid-0');
+		await probeValidator.validateProbe('measurement-id', 'test-id-1', 'probe-uuid-1');
 	});
 
 	it('should throw for invalid probe id', async () => {
 		probeValidator.addValidIds('measurement-id', 'test-id', 'probe-uuid');
 		const error = await probeValidator.validateProbe('measurement-id', 'test-id', 'invalid-probe-uuid').catch(err => err);
-		expect(error.message).to.equal('Probe ID is wrong for key measurement-id_test-id. Expected: probe-uuid, actual: invalid-probe-uuid');
+		expect(error.message).to.equal('Probe ID is wrong for measurement ID: measurement-id, test ID: test-id. Expected: probe-uuid, actual: invalid-probe-uuid');
 	});
 
 	it('should throw for missing key', async () => {
 		const error = await probeValidator.validateProbe('missing-measurement-id', 'test-id', 'probe-uuid').catch(err => err);
-		expect(error.message).to.equal('Probe ID not found for key missing-measurement-id_test-id');
+		expect(error.message).to.equal('Probe ID not found for measurement ID: missing-measurement-id, test ID: test-id');
 	});
 
 	it('should search key in redis if not found locally', async () => {
@@ -36,6 +38,6 @@ describe('ProbeValidator', () => {
 	it('should throw if redis probe id is different', async () => {
 		redis.hGet.resolves('different-probe-uuid');
 		const error = await probeValidator.validateProbe('only-redis-measurement-id', 'test-id', 'probe-uuid').catch(err => err);
-		expect(error.message).to.equal('Probe ID is wrong for key only-redis-measurement-id_test-id. Expected: different-probe-uuid, actual: probe-uuid');
+		expect(error.message).to.equal('Probe ID is wrong for measurement ID: only-redis-measurement-id, test ID: test-id. Expected: different-probe-uuid, actual: probe-uuid');
 	});
 });