diff --git a/internal/metrics.go b/internal/metrics.go
new file mode 100644
index 0000000..f826704
--- /dev/null
+++ b/internal/metrics.go
@@ -0,0 +1,21 @@
+package internal
+
+// Counters is a trivial in-memory metrics registry for the demo service.
+type Counters struct {
+	counts map[string]int
+}
+
+// NewCounters constructs an empty Counters.
+func NewCounters() *Counters {
+	return &Counters{counts: make(map[string]int)}
+}
+
+// Incr increments the named counter by 1.
+func (c *Counters) Incr(name string) {
+	c.counts[name]++
+}
+
+// Value returns the current value of the named counter.
+func (c *Counters) Value(name string) int {
+	return c.counts[name]
+}