diff --git a/internal/domain/rsvp.go b/internal/domain/rsvp.go
new file mode 100644
index 0000000..21231a0
--- /dev/null
+++ b/internal/domain/rsvp.go
@@ -0,0 +1,57 @@
+package domain
+
+import (
+	"fmt"
+	"net/http"
+	"strings"
+
+	"golang.org/x/xerrors"
+)
+
+// RSVP represent a enum status relation to some event.
+type RSVP struct {
+	rsvp string
+}
+
+var (
+	RSVPUnd        RSVP = RSVP{}             // "und"
+	RSVPInterested RSVP = RSVP{"interested"} // "interested"
+	RSVPMaybe      RSVP = RSVP{"maybe"}      // "maybe"
+	RSVPNo         RSVP = RSVP{"no"}         // "no"
+	RSVPYes        RSVP = RSVP{"yes"}        // "yes"
+)
+
+var ErrRSVPSyntax error = Error{
+	Description: fmt.Sprintf("got unsupported RSVP enum value, expect '%s', '%s', '%s' or '%s'", RSVPInterested,
+		RSVPMaybe, RSVPNo, RSVPYes),
+	Frame: xerrors.Caller(1),
+	Code:  http.StatusBadRequest,
+}
+
+var stringsRSVPs = map[string]RSVP{
+	RSVPInterested.rsvp: RSVPInterested,
+	RSVPMaybe.rsvp:      RSVPMaybe,
+	RSVPNo.rsvp:         RSVPNo,
+	RSVPYes.rsvp:        RSVPYes,
+}
+
+func ParseRSVP(v string) (RSVP, error) {
+	// NOTE(toby3d): Case-insensitive values, normalized to lowercase.
+	if out, ok := stringsRSVPs[strings.ToLower(v)]; ok {
+		return out, nil
+	}
+
+	return RSVPUnd, fmt.Errorf("cannot parse '%s' as RSVP enum: %w", v, ErrRSVPSyntax)
+}
+
+func (rsvp RSVP) String() string {
+	if rsvp.rsvp != "" {
+		return rsvp.rsvp
+	}
+
+	return "und"
+}
+
+func (rsvp RSVP) GoString() string {
+	return "domain.RSVP(" + rsvp.String() + ")"
+}