diff --git a/docs/adr/0014-pan-redaction-payment-method-aggregate-and-idempotency-key.md b/docs/adr/0014-pan-redaction-payment-method-aggregate-and-idempotency-key.md
index 5389e68..faff93a 100644
--- a/docs/adr/0014-pan-redaction-payment-method-aggregate-and-idempotency-key.md
+++ b/docs/adr/0014-pan-redaction-payment-method-aggregate-and-idempotency-key.md
@@ -31,3 +31,7 @@ Two smaller decisions follow from the same logic. A **blank header is treated as
 ## Consequences
 
 No new infrastructure and no new dependency: tokenization is a UUID and a `last_four`, dedupe is one table and one SHA-256. Cost is zero. The honest limits are recorded so they are not mistaken for finished work: the `vault_ref` is a placeholder, not a real external vault; tokens are not yet reused across a customer's orders (every checkout mints a new one), which is fine for a simulator but is the obvious next deepening if a real provider is wired in Phase 15; and the idempotency table grows unbounded until a retention sweep is added. **PragProg reversibility** — both features are additive and the header is optional, so nothing here forecloses a later move to a real tokenization provider or a managed idempotency layer.
+
+## Update — idempotency retention sweep (#73, 2026-06-05)
+
+The "grows unbounded" limitation above is now closed. `IdempotencyRetention` runs a scheduled sweep (`@EnableScheduling`, fixed delay `shopsphere.ordering.idempotency.sweep-interval`, default `PT1H`) that issues `DELETE FROM ordering.idempotency_keys WHERE created_at < now() − ttl`, where the TTL is `shopsphere.ordering.idempotency.ttl` (default `PT24H`). Flyway `V13` adds an index on `created_at` so the periodic delete finds expired rows without a full scan. The 24h default is a wide margin over the seconds-to-minutes a legitimate client retry takes, so the sweep never races a live dedupe: by the time a claim is eligible for deletion, no in-flight request could still reference it, and a retry arriving after expiry correctly places a fresh order. **XP YAGNI / PragProg** — this is the minimum that bounds the table (one scheduled `DELETE`, one index, two config knobs), not a partitioning or external-TTL scheme; the cutoff and cadence are properties, so tightening them later is a config change, not a redeploy of logic. The sweep is driven through a package-private `sweep()` method so the integration test can run it deterministically (backdated key → swept; fresh key survives), and the Phase-14 `IdempotencyKeyIT` dedup scenarios stay green because the default TTL is far larger than any test's lifetime.
diff --git a/docs/modulith/components.puml b/docs/modulith/components.puml
index 8acff6d..925b8b1 100644
--- a/docs/modulith/components.puml
+++ b/docs/modulith/components.puml
@@ -16,12 +16,12 @@ Container_Boundary("ShopSphere.ShopSphere_boundary", "ShopSphere", $tags="") {
   Component(ShopSphere.ShopSphere.Ordering, "Ordering", $techn="Module", $descr="", $tags="", $link="")
 }
 
+Rel(ShopSphere.ShopSphere.Ordering, ShopSphere.ShopSphere.Common, "depends on", $techn="", $tags="", $link="")
 Rel(ShopSphere.ShopSphere.Ordering, ShopSphere.ShopSphere.Catalog, "uses", $techn="", $tags="", $link="")
 Rel(ShopSphere.ShopSphere.Ordering, ShopSphere.ShopSphere.Payment, "uses", $techn="", $tags="", $link="")
-Rel(ShopSphere.ShopSphere.Payment, ShopSphere.ShopSphere.Common, "depends on", $techn="", $tags="", $link="")
 Rel(ShopSphere.ShopSphere.Catalog, ShopSphere.ShopSphere.Common, "depends on", $techn="", $tags="", $link="")
+Rel(ShopSphere.ShopSphere.Payment, ShopSphere.ShopSphere.Common, "depends on", $techn="", $tags="", $link="")
 Rel(ShopSphere.ShopSphere.Ordering, ShopSphere.ShopSphere.Identity, "depends on", $techn="", $tags="", $link="")
-Rel(ShopSphere.ShopSphere.Ordering, ShopSphere.ShopSphere.Common, "depends on", $techn="", $tags="", $link="")
 
 SHOW_LEGEND(true)
 @enduml
\ No newline at end of file
diff --git a/docs/modulith/module-ordering.puml b/docs/modulith/module-ordering.puml
index d37d337..bd113fa 100644
--- a/docs/modulith/module-ordering.puml
+++ b/docs/modulith/module-ordering.puml
@@ -16,12 +16,12 @@ Container_Boundary("ShopSphere.ShopSphere_boundary", "ShopSphere", $tags="") {
   Component(ShopSphere.ShopSphere.Ordering, "Ordering", $techn="Module", $descr="", $tags="", $link="")
 }
 
+Rel(ShopSphere.ShopSphere.Ordering, ShopSphere.ShopSphere.Common, "depends on", $techn="", $tags="", $link="")
 Rel(ShopSphere.ShopSphere.Ordering, ShopSphere.ShopSphere.Catalog, "uses", $techn="", $tags="", $link="")
 Rel(ShopSphere.ShopSphere.Ordering, ShopSphere.ShopSphere.Payment, "uses", $techn="", $tags="", $link="")
-Rel(ShopSphere.ShopSphere.Payment, ShopSphere.ShopSphere.Common, "depends on", $techn="", $tags="", $link="")
 Rel(ShopSphere.ShopSphere.Catalog, ShopSphere.ShopSphere.Common, "depends on", $techn="", $tags="", $link="")
+Rel(ShopSphere.ShopSphere.Payment, ShopSphere.ShopSphere.Common, "depends on", $techn="", $tags="", $link="")
 Rel(ShopSphere.ShopSphere.Ordering, ShopSphere.ShopSphere.Identity, "depends on", $techn="", $tags="", $link="")
-Rel(ShopSphere.ShopSphere.Ordering, ShopSphere.ShopSphere.Common, "depends on", $techn="", $tags="", $link="")
 
 SHOW_LEGEND(true)
 @enduml
\ No newline at end of file
diff --git a/src/main/java/com/shopsphere/ordering/IdempotencyKeys.java b/src/main/java/com/shopsphere/ordering/IdempotencyKeys.java
index ac1c364..d7ae4f4 100644
--- a/src/main/java/com/shopsphere/ordering/IdempotencyKeys.java
+++ b/src/main/java/com/shopsphere/ordering/IdempotencyKeys.java
@@ -3,6 +3,8 @@
 import org.springframework.jdbc.core.JdbcTemplate;
 import org.springframework.stereotype.Component;
 
+import java.sql.Timestamp;
+import java.time.Instant;
 import java.util.Optional;
 import java.util.UUID;
 
@@ -41,6 +43,17 @@ Optional<PriorRequest> find(UUID customerId, String key) {
                 customerId, key).stream().findFirst();
     }
 
+    /**
+     * Deletes every claim created strictly before {@code cutoff} and returns how many rows went.
+     * Used by the retention sweep ({@link IdempotencyRetention}) to keep the table from growing
+     * unbounded; the cutoff only needs to predate any legitimate client-retry window.
+     */
+    int deleteOlderThan(Instant cutoff) {
+        return jdbc.update(
+                "DELETE FROM ordering.idempotency_keys WHERE created_at < ?",
+                Timestamp.from(cutoff));
+    }
+
     record PriorRequest(String requestHash, UUID orderId) {
     }
 }
diff --git a/src/main/java/com/shopsphere/ordering/IdempotencyRetention.java b/src/main/java/com/shopsphere/ordering/IdempotencyRetention.java
new file mode 100644
index 0000000..55f6426
--- /dev/null
+++ b/src/main/java/com/shopsphere/ordering/IdempotencyRetention.java
@@ -0,0 +1,58 @@
+package com.shopsphere.ordering;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.scheduling.annotation.Scheduled;
+import org.springframework.stereotype.Component;
+
+import java.time.Clock;
+import java.time.Duration;
+import java.time.Instant;
+
+/**
+ * Bounds the growth of {@code ordering.idempotency_keys}. Every keyed {@code POST /api/v1/orders}
+ * inserts a row and the placement path never removes it, so without this sweep the table and its
+ * primary-key index grow forever — the honest limitation deferred in ADR-0014 (issue #73).
+ * <p>
+ * The sweep deletes any claim older than {@code shopsphere.ordering.idempotency.ttl}. That TTL only
+ * has to outlast the window in which a client might legitimately retry the same request (seconds to
+ * minutes), so the 24h default leaves a wide safety margin while still capping retention. Dropping
+ * an old claim is safe: a retry arriving after expiry simply places a fresh order, which is the
+ * correct behaviour once no in-flight request could still be referencing the key.
+ */
+@Component
+class IdempotencyRetention {
+
+    private static final Logger log = LoggerFactory.getLogger(IdempotencyRetention.class);
+
+    private final IdempotencyKeys keys;
+    private final Duration ttl;
+    private final Clock clock;
+
+    IdempotencyRetention(IdempotencyKeys keys,
+                         @Value("${shopsphere.ordering.idempotency.ttl:PT24H}") Duration ttl,
+                         Clock clock) {
+        this.keys = keys;
+        this.ttl = ttl;
+        this.clock = clock;
+    }
+
+    /**
+     * Deletes idempotency claims older than the TTL and returns how many were removed. Package-private
+     * so it can be driven deterministically from a test; the schedule below only delegates here.
+     */
+    int sweep() {
+        Instant cutoff = clock.instant().minus(ttl);
+        int removed = keys.deleteOlderThan(cutoff);
+        if (removed > 0) {
+            log.info("Idempotency retention sweep removed {} expired key(s) older than {}", removed, cutoff);
+        }
+        return removed;
+    }
+
+    @Scheduled(fixedDelayString = "${shopsphere.ordering.idempotency.sweep-interval:PT1H}")
+    void scheduledSweep() {
+        sweep();
+    }
+}
diff --git a/src/main/java/com/shopsphere/ordering/OrderingConfig.java b/src/main/java/com/shopsphere/ordering/OrderingConfig.java
new file mode 100644
index 0000000..4f15223
--- /dev/null
+++ b/src/main/java/com/shopsphere/ordering/OrderingConfig.java
@@ -0,0 +1,13 @@
+package com.shopsphere.ordering;
+
+import org.springframework.context.annotation.Configuration;
+import org.springframework.scheduling.annotation.EnableScheduling;
+
+/**
+ * Turns on Spring's scheduler so {@link IdempotencyRetention#scheduledSweep()} fires. Scoped to the
+ * Ordering module rather than the application class to keep the concern next to its only user.
+ */
+@Configuration
+@EnableScheduling
+class OrderingConfig {
+}
diff --git a/src/main/resources/application.yml b/src/main/resources/application.yml
index 501e7e3..9fbf171 100644
--- a/src/main/resources/application.yml
+++ b/src/main/resources/application.yml
@@ -63,3 +63,10 @@ shopsphere:
     ttl: PT15M
   refresh:
     ttl: P7D
+  ordering:
+    idempotency:
+      # Delete idempotency claims older than this. Must outlast any legitimate client-retry window;
+      # 24h is a wide margin over the seconds-to-minutes a real retry takes (#73, ADR-0014).
+      ttl: PT24H
+      # How often the retention sweep runs (fixed delay between completions).
+      sweep-interval: PT1H
diff --git a/src/main/resources/db/migration/ordering/V13__idempotency_keys_created_at_index.sql b/src/main/resources/db/migration/ordering/V13__idempotency_keys_created_at_index.sql
new file mode 100644
index 0000000..92ca37a
--- /dev/null
+++ b/src/main/resources/db/migration/ordering/V13__idempotency_keys_created_at_index.sql
@@ -0,0 +1,5 @@
+-- Retention sweep (#73, deferred from ADR-0014) deletes idempotency claims by age:
+-- DELETE FROM ordering.idempotency_keys WHERE created_at < <cutoff>. The primary key is on
+-- (customer_id, idempotency_key), so that predicate would otherwise scan the whole table on every
+-- sweep. This index lets the periodic DELETE find expired rows without a full scan.
+CREATE INDEX idx_idempotency_keys_created_at ON ordering.idempotency_keys (created_at);
diff --git a/src/test/java/com/shopsphere/ordering/IdempotencyRetentionIT.java b/src/test/java/com/shopsphere/ordering/IdempotencyRetentionIT.java
new file mode 100644
index 0000000..b420806
--- /dev/null
+++ b/src/test/java/com/shopsphere/ordering/IdempotencyRetentionIT.java
@@ -0,0 +1,67 @@
+package com.shopsphere.ordering;
+
+import com.shopsphere.SharedContainers;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.jdbc.core.JdbcTemplate;
+import org.springframework.test.context.DynamicPropertyRegistry;
+import org.springframework.test.context.DynamicPropertySource;
+
+import java.sql.Timestamp;
+import java.time.Duration;
+import java.time.Instant;
+import java.util.UUID;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Retention sweep for {@code ordering.idempotency_keys} (#73, deferred from ADR-0014). A key older
+ * than the configured TTL is deleted by the sweep; a key inside the window survives untouched.
+ */
+@SpringBootTest
+class IdempotencyRetentionIT {
+
+    @DynamicPropertySource
+    static void containers(DynamicPropertyRegistry registry) {
+        SharedContainers.registerProperties(registry);
+    }
+
+    @Autowired
+    IdempotencyRetention retention;
+
+    @Autowired
+    JdbcTemplate jdbc;
+
+    @Test
+    void sweepRemovesExpiredKeysButKeepsFreshOnes() {
+        UUID customer = UUID.randomUUID();
+        String staleKey = "stale-" + UUID.randomUUID();
+        String freshKey = "fresh-" + UUID.randomUUID();
+        Instant now = Instant.now();
+
+        insertKey(customer, staleKey, now.minus(Duration.ofHours(48)));
+        insertKey(customer, freshKey, now);
+
+        retention.sweep();
+
+        assertThat(rowExists(customer, staleKey)).isFalse();
+        assertThat(rowExists(customer, freshKey)).isTrue();
+    }
+
+    private void insertKey(UUID customer, String key, Instant createdAt) {
+        jdbc.update(
+                "INSERT INTO ordering.idempotency_keys "
+                        + "(customer_id, idempotency_key, request_hash, order_id, created_at) "
+                        + "VALUES (?, ?, ?, ?, ?)",
+                customer, key, "hash", UUID.randomUUID(), Timestamp.from(createdAt));
+    }
+
+    private boolean rowExists(UUID customer, String key) {
+        Integer count = jdbc.queryForObject(
+                "SELECT count(*) FROM ordering.idempotency_keys "
+                        + "WHERE customer_id = ? AND idempotency_key = ?",
+                Integer.class, customer, key);
+        return count != null && count > 0;
+    }
+}