diff --git a/util/echo.go b/util/echo.go
index 68b2cfb..860a9a7 100644
--- a/util/echo.go
+++ b/util/echo.go
@@ -1,6 +1,11 @@
 package util
 
-import "github.com/labstack/echo/v4"
+import (
+	"errors"
+	"github.com/jackc/pgx/v5"
+	"github.com/labstack/echo/v4"
+	"net/http"
+)
 
 func EchoAllParams[T any](c echo.Context, fn func(string) (T, error), params ...string) ([]T, error) {
 	r := make([]T, 0, len(params))
@@ -14,3 +19,11 @@ func EchoAllParams[T any](c echo.Context, fn func(string) (T, error), params ...
 
 	return r, nil
 }
+
+func NewEchoPgxHTTPError(err error) *echo.HTTPError {
+	if errors.Is(err, pgx.ErrNoRows) {
+		return echo.NewHTTPError(http.StatusNotFound, err)
+	}
+
+	return echo.NewHTTPError(http.StatusInternalServerError, err)
+}
diff --git a/util/util.go b/util/util.go
new file mode 100644
index 0000000..6217177
--- /dev/null
+++ b/util/util.go
@@ -0,0 +1,15 @@
+package util
+
+func Unique[T comparable](s []T) []T {
+	r := make([]T, 0, len(s))
+	unq := make(map[T]bool)
+
+	for _, v := range s {
+		if present, _ := unq[v]; !present {
+			unq[v] = true
+			r = append(r, v)
+		}
+	}
+
+	return r
+}
diff --git a/web/dev_application.go b/web/dev_application.go
index 4619fba..71e56d1 100644
--- a/web/dev_application.go
+++ b/web/dev_application.go
@@ -102,7 +102,7 @@ VALUES
 		})
 
 		if err != nil {
-			return echo.NewHTTPError(http.StatusInternalServerError, err)
+			return util.NewEchoPgxHTTPError(err)
 		}
 
 		return c.JSON(http.StatusOK, map[string]any{
@@ -137,7 +137,7 @@ AND id = $2
 		})
 
 		if err != nil {
-			return echo.NewHTTPError(http.StatusInternalServerError, err)
+			return util.NewEchoPgxHTTPError(err)
 		}
 
 		if !deleted {
@@ -188,7 +188,7 @@ GROUP BY apps.id
 		})
 
 		if err != nil {
-			return echo.NewHTTPError(http.StatusInternalServerError, err)
+			return util.NewEchoPgxHTTPError(err)
 		}
 
 		return c.JSON(http.StatusOK, results)
@@ -232,7 +232,7 @@ GROUP BY app.id
 		})
 
 		if err != nil {
-			return echo.NewHTTPError(http.StatusInternalServerError, err)
+			return util.NewEchoPgxHTTPError(err)
 		}
 
 		return c.JSON(http.StatusOK, result)
@@ -338,7 +338,7 @@ AND apps.account_id = $2
 		})
 
 		if err != nil {
-			return echo.NewHTTPError(http.StatusInternalServerError, err)
+			return util.NewEchoPgxHTTPError(err)
 		}
 
 		nextToken := ""
diff --git a/web/dev_application_client.go b/web/dev_application_client.go
index c12a3cc..367b56d 100644
--- a/web/dev_application_client.go
+++ b/web/dev_application_client.go
@@ -69,6 +69,7 @@ func CreateDevApplicationClientEndpoint() echo.HandlerFunc {
 			return echo.NewHTTPError(http.StatusBadRequest, errors.New("displayname must be between 1 and 100 characters"))
 		}
 
+		body.RedirectURIs = util.Unique(body.RedirectURIs)
 		if len(body.RedirectURIs) < 1 || len(body.RedirectURIs) > 50 {
 			return echo.NewHTTPError(http.StatusBadRequest, errors.New("at least one and at most 50 redirect URIs might be added"))
 		}
@@ -139,7 +140,7 @@ AND id = $2
 		})
 
 		if err != nil {
-			return echo.NewHTTPError(http.StatusInternalServerError, err)
+			return util.NewEchoPgxHTTPError(err)
 		}
 
 		if !created {
@@ -197,7 +198,7 @@ AND app_clients.id = $3
 		})
 
 		if err != nil {
-			return echo.NewHTTPError(http.StatusInternalServerError, err)
+			return util.NewEchoPgxHTTPError(err)
 		}
 
 		return c.JSON(http.StatusOK, result)
@@ -251,7 +252,7 @@ WHERE id = (
 		})
 
 		if err != nil {
-			return echo.NewHTTPError(http.StatusInternalServerError, err)
+			return util.NewEchoPgxHTTPError(err)
 		}
 
 		if !updated {
@@ -286,17 +287,24 @@ func AddOrDeleteDevApplicationClientRedirectURIEndpoint() echo.HandlerFunc {
 		if c.Request().Method == http.MethodDelete {
 			sql = `
 UPDATE application_clients
-SET redirect_uris = ARRAY_REMOVE(redirect_uris, $4)
-WHERE id = (
-    SELECT app_clients.id
+SET redirect_uris = prep.redirect_uris
+FROM (
+	SELECT
+		app_clients.id AS id,
+		CASE
+			WHEN ARRAY_POSITION(app_clients.redirect_uris, $4) IS NOT NULL THEN ARRAY_REMOVE(app_clients.redirect_uris, $4)
+			ELSE app_clients.redirect_uris
+		END AS redirect_uris,
+	    app_clients.redirect_uris AS prev_redirect_uris
     FROM application_clients app_clients
     INNER JOIN applications apps
     ON app_clients.application_id = apps.id
     WHERE apps.account_id = $1
     AND apps.id = $2
     AND app_clients.id = $3
-    AND ARRAY_POSITION(app_clients.redirect_uris, $4) IS NOT NULL
-)
+) prep
+WHERE application_clients.id = prep.id
+RETURNING prep.prev_redirect_uris, application_clients.redirect_uris
 `
 		} else {
 			if err := validateRedirectURIs([]string{redirectUri}); err != nil {
@@ -305,39 +313,43 @@ WHERE id = (
 
 			sql = `
 UPDATE application_clients
-SET redirect_uris = ARRAY_APPEND(redirect_uris, $4)
-WHERE id = (
-    SELECT app_clients.id
+SET redirect_uris = prep.redirect_uris
+FROM (
+	SELECT
+		app_clients.id AS id,
+		CASE
+			WHEN ARRAY_POSITION(app_clients.redirect_uris, $4) IS NULL THEN ARRAY_APPEND(app_clients.redirect_uris, $4)
+			ELSE app_clients.redirect_uris
+		END AS redirect_uris,
+	    app_clients.redirect_uris AS prev_redirect_uris
     FROM application_clients app_clients
     INNER JOIN applications apps
     ON app_clients.application_id = apps.id
     WHERE apps.account_id = $1
     AND apps.id = $2
     AND app_clients.id = $3
-    AND ARRAY_POSITION(app_clients.redirect_uris, $4) IS NULL
-)
+) prep
+WHERE application_clients.id = prep.id
+RETURNING prep.prev_redirect_uris, application_clients.redirect_uris
 `
 		}
 
 		ctx := c.Request().Context()
 
-		var updated bool
+		var prevRedirectURIs, newRedirectURIs []string
 		err := rctx.ExecuteTx(ctx, pgx.TxOptions{}, func(tx pgx.Tx) error {
-			tag, err := tx.Exec(ctx, sql, session.AccountId, applicationId, clientId, redirectUri)
-			if err != nil {
-				return err
-			}
-
-			updated = tag.RowsAffected() > 0
-			return nil
+			return tx.QueryRow(ctx, sql, session.AccountId, applicationId, clientId, redirectUri).Scan(
+				&prevRedirectURIs,
+				&newRedirectURIs,
+			)
 		})
 
 		if err != nil {
-			return echo.NewHTTPError(http.StatusInternalServerError, err)
+			return util.NewEchoPgxHTTPError(err)
 		}
 
-		if !updated {
-			return echo.NewHTTPError(http.StatusNotFound, errors.New("no rows were updated"))
+		if slices.Equal(prevRedirectURIs, newRedirectURIs) {
+			return c.NoContent(http.StatusNotModified)
 		}
 
 		return c.JSON(http.StatusOK, map[string]string{})
@@ -379,7 +391,7 @@ WHERE id = (
 		})
 
 		if err != nil {
-			return echo.NewHTTPError(http.StatusInternalServerError, err)
+			return util.NewEchoPgxHTTPError(err)
 		}
 
 		if !deleted {
@@ -442,7 +454,7 @@ AND application_client_accounts.account_id = app_client_account.account_id
 		})
 
 		if err != nil {
-			return echo.NewHTTPError(http.StatusInternalServerError, err)
+			return util.NewEchoPgxHTTPError(err)
 		}
 
 		if !updated {
diff --git a/web/gw2_account.go b/web/gw2_account.go
index be67970..26a81a8 100644
--- a/web/gw2_account.go
+++ b/web/gw2_account.go
@@ -5,6 +5,7 @@ import (
 	"github.com/gofrs/uuid/v5"
 	"github.com/gw2auth/gw2auth.com-api/service"
 	"github.com/gw2auth/gw2auth.com-api/service/gw2"
+	"github.com/gw2auth/gw2auth.com-api/util"
 	"github.com/jackc/pgx/v5"
 	"github.com/labstack/echo/v4"
 	"go.uber.org/zap"
@@ -124,7 +125,7 @@ GROUP BY gw2_acc.gw2_account_id
 			return err
 		})
 		if err != nil {
-			return err
+			return util.NewEchoPgxHTTPError(err)
 		}
 
 		return c.JSON(http.StatusOK, results)
@@ -206,7 +207,7 @@ GROUP BY gw2_acc.gw2_account_id
 			)
 		})
 		if err != nil {
-			return err
+			return util.NewEchoPgxHTTPError(err)
 		}
 
 		if verified {
@@ -271,7 +272,7 @@ WHERE account_id = $1 AND gw2_account_id = $2
 		})
 
 		if err != nil {
-			return err
+			return util.NewEchoPgxHTTPError(err)
 		}
 
 		if rowsAffected < 1 {
diff --git a/web/gw2_api_token.go b/web/gw2_api_token.go
index 793e2e7..5907559 100644
--- a/web/gw2_api_token.go
+++ b/web/gw2_api_token.go
@@ -5,6 +5,7 @@ import (
 	"github.com/gofrs/uuid/v5"
 	"github.com/gw2auth/gw2auth.com-api/service"
 	"github.com/gw2auth/gw2auth.com-api/service/gw2"
+	"github.com/gw2auth/gw2auth.com-api/util"
 	"github.com/its-felix/shine"
 	"github.com/jackc/pgx/v5"
 	"github.com/labstack/echo/v4"
@@ -150,7 +151,7 @@ last_valid_check_time = EXCLUDED.last_valid_check_time
 			if errors.As(err, &httpError) {
 				return httpError
 			} else {
-				return echo.NewHTTPError(http.StatusInternalServerError, err)
+				return util.NewEchoPgxHTTPError(err)
 			}
 		}
 
@@ -181,7 +182,7 @@ AND gw2_account_id = $2
 		})
 
 		if err != nil {
-			return echo.NewHTTPError(http.StatusInternalServerError, err)
+			return util.NewEchoPgxHTTPError(err)
 		}
 
 		return c.JSON(http.StatusOK, map[string]string{})
diff --git a/web/summary.go b/web/summary.go
index c25493c..fd3b161 100644
--- a/web/summary.go
+++ b/web/summary.go
@@ -1,6 +1,7 @@
 package web
 
 import (
+	"github.com/gw2auth/gw2auth.com-api/util"
 	"github.com/jackc/pgx/v5"
 	"github.com/labstack/echo/v4"
 	"net/http"
@@ -41,7 +42,7 @@ SELECT
 		})
 
 		if err != nil {
-			return echo.NewHTTPError(http.StatusInternalServerError, err)
+			return util.NewEchoPgxHTTPError(err)
 		}
 
 		return c.JSON(http.StatusOK, res)
diff --git a/web/user_application.go b/web/user_application.go
index f0ae1ad..1fe12e8 100644
--- a/web/user_application.go
+++ b/web/user_application.go
@@ -3,6 +3,7 @@ package web
 import (
 	"github.com/gofrs/uuid/v5"
 	"github.com/gw2auth/gw2auth.com-api/service"
+	"github.com/gw2auth/gw2auth.com-api/util"
 	"github.com/jackc/pgx/v5"
 	"github.com/labstack/echo/v4"
 	"net/http"
@@ -72,7 +73,7 @@ GROUP BY app.id
 		})
 
 		if err != nil {
-			return echo.NewHTTPError(http.StatusInternalServerError, err)
+			return util.NewEchoPgxHTTPError(err)
 		}
 
 		return c.JSON(http.StatusOK, results)
@@ -98,7 +99,7 @@ AND application_id = $2
 		})
 
 		if err != nil {
-			return echo.NewHTTPError(http.StatusInternalServerError, err)
+			return util.NewEchoPgxHTTPError(err)
 		}
 
 		return c.JSON(http.StatusOK, map[string]string{})