diff --git a/plugins/catalog-backend/src/catalog/DatabaseEntitiesCatalog.ts b/plugins/catalog-backend/src/catalog/DatabaseEntitiesCatalog.ts
index 697da0ea35..fb19f04220 100644
--- a/plugins/catalog-backend/src/catalog/DatabaseEntitiesCatalog.ts
+++ b/plugins/catalog-backend/src/catalog/DatabaseEntitiesCatalog.ts
@@ -17,14 +17,14 @@
 import { NotFoundError } from '@backstage/backend-common';
 import { Database } from '../database';
 import { DescriptorEnvelope } from '../ingestion/types';
-import { EntitiesCatalog } from './types';
+import { EntitiesCatalog, EntityFilters } from './types';
 
 export class DatabaseEntitiesCatalog implements EntitiesCatalog {
   constructor(private readonly database: Database) {}
 
-  async entities(): Promise<DescriptorEnvelope[]> {
+  async entities(filters?: EntityFilters): Promise<DescriptorEnvelope[]> {
     const items = await this.database.transaction(tx =>
-      this.database.entities(tx),
+      this.database.entities(tx, filters),
     );
     return items.map(i => i.entity);
   }
diff --git a/plugins/catalog-backend/src/catalog/types.ts b/plugins/catalog-backend/src/catalog/types.ts
index 92c059d25b..e5beb801d0 100644
--- a/plugins/catalog-backend/src/catalog/types.ts
+++ b/plugins/catalog-backend/src/catalog/types.ts
@@ -18,11 +18,17 @@ import * as yup from 'yup';
 import { DescriptorEnvelope } from '../ingestion';
 
 //
-// Items
+// Entities
 //
 
+export type EntityFilter = {
+  key: string;
+  values: (string | null)[];
+};
+export type EntityFilters = EntityFilter[];
+
 export type EntitiesCatalog = {
-  entities(): Promise<DescriptorEnvelope[]>;
+  entities(filters?: EntityFilters): Promise<DescriptorEnvelope[]>;
   entity(
     kind: string,
     name: string,
diff --git a/plugins/catalog-backend/src/database/Database.test.ts b/plugins/catalog-backend/src/database/Database.test.ts
index 0eb64916e5..7f02b45eee 100644
--- a/plugins/catalog-backend/src/database/Database.test.ts
+++ b/plugins/catalog-backend/src/database/Database.test.ts
@@ -28,6 +28,7 @@ import {
   DbEntityResponse,
   DbLocationsRow,
 } from './types';
+import { DescriptorEnvelope } from '../ingestion';
 
 describe('Database', () => {
   let database: Knex;
@@ -242,4 +243,107 @@ describe('Database', () => {
       ).rejects.toThrow(ConflictError);
     });
   });
+
+  describe('entities', () => {
+    it('can get all entities with empty filters list', async () => {
+      const catalog = new Database(database, getVoidLogger());
+      const e1: DescriptorEnvelope = { apiVersion: 'a', kind: 'b' };
+      const e2: DescriptorEnvelope = {
+        apiVersion: 'a',
+        kind: 'b',
+        spec: { c: null },
+      };
+      await catalog.transaction(async tx => {
+        await catalog.addEntity(tx, { entity: e1 });
+        await catalog.addEntity(tx, { entity: e2 });
+      });
+      await expect(
+        catalog.transaction(async tx => catalog.entities(tx, [])),
+      ).resolves.toEqual([
+        { locationId: undefined, entity: expect.objectContaining(e1) },
+        { locationId: undefined, entity: expect.objectContaining(e2) },
+      ]);
+    });
+    it('can get all specific entities for matching filters (naive case)', async () => {
+      const catalog = new Database(database, getVoidLogger());
+      const entities: DescriptorEnvelope[] = [
+        { apiVersion: 'a', kind: 'b' },
+        {
+          apiVersion: 'a',
+          kind: 'b',
+          spec: { c: 'some' },
+        },
+        {
+          apiVersion: 'a',
+          kind: 'b',
+          spec: { c: null },
+        },
+      ];
+
+      await catalog.transaction(async tx => {
+        for (const entity of entities) {
+          await catalog.addEntity(tx, { entity });
+        }
+      });
+
+      await expect(
+        catalog.transaction(async tx =>
+          catalog.entities(tx, [
+            { key: 'kind', values: ['b'] },
+            { key: 'spec.c', values: ['some'] },
+          ]),
+        ),
+      ).resolves.toEqual([
+        { locationId: undefined, entity: expect.objectContaining(entities[1]) },
+      ]);
+    });
+
+    it('can get all specific entities for matching filters with nulls (both missing and literal null value)', async () => {
+      const catalog = new Database(database, getVoidLogger());
+      const entities: DescriptorEnvelope[] = [
+        { apiVersion: 'a', kind: 'b' },
+        {
+          apiVersion: 'a',
+          kind: 'b',
+          spec: { c: 'some' },
+        },
+        {
+          apiVersion: 'a',
+          kind: 'b',
+          spec: { c: null },
+        },
+      ];
+
+      await catalog.transaction(async tx => {
+        for (const entity of entities) {
+          await catalog.addEntity(tx, { entity });
+        }
+      });
+
+      const rows = await catalog.transaction(async tx =>
+        catalog.entities(tx, [
+          { key: 'kind', values: ['b'] },
+          { key: 'spec.c', values: [null, 'some'] },
+        ]),
+      );
+
+      expect(rows.length).toEqual(3);
+      expect(rows).toEqual(
+        expect.arrayContaining([
+          {
+            locationId: undefined,
+            entity: expect.objectContaining(entities[0]),
+          },
+          {
+            locationId: undefined,
+            entity: expect.objectContaining(entities[1]),
+          },
+          {
+            locationId: undefined,
+            entity: expect.objectContaining(entities[2]),
+          },
+        ]),
+      );
+    });
+  });
 });
diff --git a/plugins/catalog-backend/src/database/Database.ts b/plugins/catalog-backend/src/database/Database.ts
index cd4ca731a3..3b616b4202 100644
--- a/plugins/catalog-backend/src/database/Database.ts
+++ b/plugins/catalog-backend/src/database/Database.ts
@@ -23,6 +23,7 @@ import Knex from 'knex';
 import lodash from 'lodash';
 import { v4 as uuidv4 } from 'uuid';
 import { Logger } from 'winston';
+import { EntityFilters } from '../catalog';
 import { DescriptorEnvelope, EntityMeta } from '../ingestion';
 import { buildEntitySearch } from './search';
 import {
@@ -309,10 +310,30 @@ export class Database {
     return { locationId: request.locationId, entity: newEntity };
   }
 
-  async entities(tx: Knex.Transaction<any, any>): Promise<DbEntityResponse[]> {
-    const rows = await tx<DbEntitiesRow>('entities')
+  async entities(
+    tx: Knex.Transaction<any, any>,
+    filters?: EntityFilters,
+  ): Promise<DbEntityResponse[]> {
+    let builder = tx<DbEntitiesRow>('entities');
+    for (const [index, filter] of (filters ?? []).entries()) {
+      builder = builder
+        .leftOuterJoin(`entities_search as t${index}`, function join() {
+          this.on('entities.id', '=', `t${index}.entity_id`).onIn(
+            `t${index}.value`,
+            filter.values.filter(x => x),
+          );
+          if (filter.values.some(x => !x)) {
+            this.orOnNull(`t${index}.value`);
+          }
+        })
+        .where(`t${index}.key`, '=', filter.key);
+    }
+
+    const rows = await builder
       .orderBy('namespace', 'name')
-      .select();
+      .select('entities.*')
+      .groupBy('id');
+
     return rows.map(row => toEntityResponse(row));
   }
 
diff --git a/plugins/catalog-backend/src/service/router.test.ts b/plugins/catalog-backend/src/service/router.test.ts
index c4e21c9b0e..1b1f4c5034 100644
--- a/plugins/catalog-backend/src/service/router.test.ts
+++ b/plugins/catalog-backend/src/service/router.test.ts
@@ -14,12 +14,16 @@
  * limitations under the License.
  */
 
+import {
+  errorHandler,
+  getVoidLogger,
+  InputError,
+} from '@backstage/backend-common';
 import express from 'express';
 import request from 'supertest';
-import { createRouter } from './router';
-import { EntitiesCatalog, LocationsCatalog, Location } from '../catalog';
-import { getVoidLogger } from '@backstage/backend-common';
+import { EntitiesCatalog, Location, LocationsCatalog } from '../catalog';
 import { DescriptorEnvelope } from '../ingestion';
+import { createRouter } from './router';
 
 class MockEntitiesCatalog implements EntitiesCatalog {
   entities = jest.fn();
@@ -50,7 +54,26 @@ describe('createRouter', () => {
       const response = await request(app).get('/entities');
 
       expect(response.status).toEqual(200);
-      expect(JSON.parse(response.text)).toEqual(entities);
+      expect(response.body).toEqual(entities);
+    });
+
+    it('parses single and multiple request parameters and passes them down', async () => {
+      const catalog = new MockEntitiesCatalog();
+
+      const router = await createRouter({
+        entitiesCatalog: catalog,
+        logger: getVoidLogger(),
+      });
+
+      const app = express().use(router);
+      const response = await request(app).get('/entities?a=1&a=&a=3&b=4&c=');
+
+      expect(response.status).toEqual(200);
+      expect(catalog.entities).toHaveBeenCalledWith([
+        { key: 'a', values: ['1', null, '3'] },
+        { key: 'b', values: ['4'] },
+        { key: 'c', values: [null] },
+      ]);
     });
   });
 
@@ -70,7 +93,26 @@ describe('createRouter', () => {
       const response = await request(app).get('/locations');
 
       expect(response.status).toEqual(200);
-      expect(JSON.parse(response.text)).toEqual(locations);
+      expect(response.body).toEqual(locations);
+    });
+
+    it('rejects malformed locations', async () => {
+      const location = ({
+        id: 'a',
+        typez: 'b',
+        target: 'c',
+      } as unknown) as Location;
+
+      const catalog = new MockLocationsCatalog();
+      const router = await createRouter({
+        locationsCatalog: catalog,
+        logger: getVoidLogger(),
+      });
+
+      const app = express().use(router);
+      const response = await request(app).post('/locations').send(location);
+
+      expect(response.status).toEqual(400);
     });
   });
 });
diff --git a/plugins/catalog-backend/src/service/router.ts b/plugins/catalog-backend/src/service/router.ts
index af714e4026..81533adfc5 100644
--- a/plugins/catalog-backend/src/service/router.ts
+++ b/plugins/catalog-backend/src/service/router.ts
@@ -14,12 +14,14 @@
  * limitations under the License.
  */
 
+import { errorHandler } from '@backstage/backend-common';
 import express from 'express';
 import Router from 'express-promise-router';
 import { Logger } from 'winston';
 import {
   addLocationSchema,
   EntitiesCatalog,
+  EntityFilters,
   LocationsCatalog,
 } from '../catalog';
 import { validateRequestBody } from './util';
@@ -34,17 +36,33 @@ export async function createRouter(
   options: RouterOptions,
 ): Promise<express.Router> {
   const { entitiesCatalog, locationsCatalog } = options;
+
   const router = Router();
+  router.use(express.json());
 
   if (entitiesCatalog) {
-    // Entities
-    router.get('/entities', async (_req, res) => {
-      const entities = await entitiesCatalog.entities();
+    router.get('/entities', async (req, res) => {
+      const filters: EntityFilters = [];
+      for (const [key, valueOrValues] of Object.entries(req.query)) {
+        const values = Array.isArray(valueOrValues)
+          ? valueOrValues
+          : [valueOrValues];
+        if (values.some(v => typeof v !== 'string')) {
+          res.status(400).send('Complex query parameters are not supported');
+          return;
+        }
+        filters.push({
+          key,
+          values: values.map(v => v || null) as string[],
+        });
+      }
+
+      const entities = await entitiesCatalog.entities(filters);
+
       res.status(200).send(entities);
     });
   }
 
-  // Locations
   if (locationsCatalog) {
     router
       .post('/locations', async (req, res) => {
@@ -68,5 +86,6 @@ export async function createRouter(
       });
   }
 
+  router.use(errorHandler());
   return router;
 }