feat(databases): S3-compatible backup targets — offsite archives + remote restore

Phase D3. Managed databases can ship backup archives to a configured
S3-compatible destination (AWS S3, MinIO, Garage, …) while the local
copy remains intact.

- backup_targets table: owner-scoped endpoint/bucket/region/prefix +
  encrypted access/secret keys (enc:v1:, never returned, has_credentials)
- create/update probe bucket access before storing; empty keys on update
  keep stored credentials; delete refused (409) while referenced
- databases.backup_target_id assigns a target; external DBs rejected
- backup pipeline uploads via a holder container over docker cp streams;
  remote failure keeps the local archive (logged), row gets remote:true
- restore prefers the local archive; on a missing local copy it downloads
  the remote object into the backup volume first
- holder containers must be started before archive ops — docker cp does
  not resolve volume mounts on never-started (Created) containers, and
  removing the source mid-stream stalls the reader without EOF
- CLI: backup-targets list|add|update|remove|test + databases update
  --backup-target; MCP: 5 new tools; Settings UI card + per-database
  target picker + offsite badge on backups; OpenAPI + llms.txt + CLI.md

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

app/backend/internal/api/backuptargets.go

@@ -0,0 +1,506 @@
+package api
+
+import (
+	"archive/tar"
+	"bytes"
+	"context"
+	"database/sql"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+	"time"
+
+	"containr/internal/database/sqlcdb"
+	"containr/internal/docker"
+	"containr/internal/secrets"
+
+	"github.com/docker/docker/api/types/mount"
+	"github.com/gin-gonic/gin"
+	"github.com/google/uuid"
+	"github.com/minio/minio-go/v7"
+	"github.com/minio/minio-go/v7/pkg/credentials"
+)
+
+// BackupTarget is an S3-compatible archive destination. Secret keys are
+// stored encrypted and never serialized — has_credentials signals presence.
+type BackupTarget struct {
+	ID             string    `json:"id"`
+	Name           string    `json:"name"`
+	Endpoint       string    `json:"endpoint"`
+	Bucket         string    `json:"bucket"`
+	Region         string    `json:"region,omitempty"`
+	Prefix         string    `json:"prefix,omitempty"`
+	HasCredentials bool      `json:"has_credentials"`
+	UseTLS         bool      `json:"use_tls"`
+	CreatedAt      time.Time `json:"created_at"`
+	UpdatedAt      time.Time `json:"updated_at"`
+
+	accessKey string `json:"-"`
+	secretKey string `json:"-"`
+}
+
+type backupTargetRequest struct {
+	Name      string `json:"name"`
+	Endpoint  string `json:"endpoint" binding:"required"`
+	Bucket    string `json:"bucket" binding:"required"`
+	Region    string `json:"region"`
+	Prefix    string `json:"prefix"`
+	AccessKey string `json:"access_key"`
+	SecretKey string `json:"secret_key"`
+	UseTLS    *bool  `json:"use_tls"`
+}
+
+func mapBackupTargetRow(row sqlcdb.BackupTarget) BackupTarget {
+	return BackupTarget{
+		ID:             row.ID,
+		Name:           row.Name,
+		Endpoint:       row.Endpoint,
+		Bucket:         row.Bucket,
+		Region:         row.Region,
+		Prefix:         row.Prefix,
+		HasCredentials: row.SecretKey != "",
+		UseTLS:         row.UseTls,
+		CreatedAt:      databaseNullTime(row.CreatedAt),
+		UpdatedAt:      databaseNullTime(row.UpdatedAt),
+		accessKey:      secrets.Decrypt(row.AccessKey),
+		secretKey:      secrets.Decrypt(row.SecretKey),
+	}
+}
+
+// s3Client builds a client for the target. Endpoint is a bare host[:port] —
+// scheme comes from use_tls, matching MinIO/Garage/AWS conventions.
+func (t BackupTarget) s3Client() (*minio.Client, error) {
+	opts := &minio.Options{Secure: t.UseTLS, Region: t.Region}
+	if t.accessKey != "" || t.secretKey != "" {
+		opts.Creds = credentials.NewStaticV4(t.accessKey, t.secretKey, "")
+	} else {
+		opts.Creds = credentials.NewIAM("")
+	}
+	return minio.New(t.Endpoint, opts)
+}
+
+func normalizeBackupTargetRequest(req *backupTargetRequest) error {
+	req.Name = strings.TrimSpace(req.Name)
+	req.Endpoint = strings.TrimSpace(req.Endpoint)
+	req.Endpoint = strings.TrimPrefix(strings.TrimPrefix(req.Endpoint, "https://"), "http://")
+	req.Endpoint = strings.TrimSuffix(req.Endpoint, "/")
+	req.Bucket = strings.TrimSpace(req.Bucket)
+	req.Prefix = strings.Trim(strings.TrimSpace(req.Prefix), "/")
+	if req.Name == "" {
+		return errors.New("name is required")
+	}
+	if req.Endpoint == "" || req.Bucket == "" {
+		return errors.New("endpoint and bucket are required")
+	}
+	return nil
+}
+
+// probeBackupTarget verifies credentials and bucket access.
+func probeBackupTarget(ctx context.Context, t BackupTarget) (time.Duration, error) {
+	client, err := t.s3Client()
+	if err != nil {
+		return 0, err
+	}
+	start := time.Now()
+	exists, err := client.BucketExists(ctx, t.Bucket)
+	if err != nil {
+		return 0, err
+	}
+	if !exists {
+		return 0, fmt.Errorf("bucket %q not found or not accessible", t.Bucket)
+	}
+	return time.Since(start), nil
+}
+
+func (h *DatabaseHandler) ListBackupTargets(c *gin.Context) {
+	userID, ok := requireAuthenticatedUserID(c)
+	if !ok {
+		return
+	}
+	rows, err := h.queries.ListBackupTargetsByUser(c.Request.Context(), userID)
+	if err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to list backup targets"})
+		return
+	}
+	targets := make([]BackupTarget, 0, len(rows))
+	for _, row := range rows {
+		t := mapBackupTargetRow(row)
+		t.accessKey, t.secretKey = "", ""
+		targets = append(targets, t)
+	}
+	c.JSON(http.StatusOK, gin.H{"backup_targets": targets})
+}
+
+func (h *DatabaseHandler) CreateBackupTarget(c *gin.Context) {
+	userID, ok := requireAuthenticatedUserID(c)
+	if !ok {
+		return
+	}
+	var req backupTargetRequest
+	if err := c.ShouldBindJSON(&req); err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error(), "code": "VALIDATION"})
+		return
+	}
+	if err := normalizeBackupTargetRequest(&req); err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error(), "code": "VALIDATION"})
+		return
+	}
+
+	useTLS := true
+	if req.UseTLS != nil {
+		useTLS = *req.UseTLS
+	}
+	target := BackupTarget{
+		ID:        "bt_" + strings.ReplaceAll(uuid.NewString(), "-", "")[:12],
+		Name:      req.Name,
+		Endpoint:  req.Endpoint,
+		Bucket:    req.Bucket,
+		Region:    req.Region,
+		Prefix:    req.Prefix,
+		UseTLS:    useTLS,
+		accessKey: req.AccessKey,
+		secretKey: req.SecretKey,
+	}
+
+	probeCtx, cancel := context.WithTimeout(c.Request.Context(), 10*time.Second)
+	defer cancel()
+	if _, err := probeBackupTarget(probeCtx, target); err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": fmt.Sprintf("Connection check failed: %v", err), "code": "DEPENDENCY_UNAVAILABLE"})
+		return
+	}
+
+	enc := func(v string) string {
+		if v == "" {
+			return ""
+		}
+		return secrets.Encrypt(v)
+	}
+	now := sql.NullTime{Time: time.Now(), Valid: true}
+	if err := h.queries.CreateBackupTarget(c.Request.Context(), sqlcdb.CreateBackupTargetParams{
+		ID:        target.ID,
+		UserID:    userID,
+		Name:      target.Name,
+		Endpoint:  target.Endpoint,
+		Bucket:    target.Bucket,
+		Region:    target.Region,
+		Prefix:    target.Prefix,
+		AccessKey: enc(req.AccessKey),
+		SecretKey: enc(req.SecretKey),
+		UseTls:    useTLS,
+		CreatedAt: now,
+		UpdatedAt: now,
+	}); err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to create backup target"})
+		return
+	}
+	LogAudit(userID, "backup_target", target.ID, "create", map[string]interface{}{"name": req.Name, "endpoint": req.Endpoint, "bucket": req.Bucket})
+	target.accessKey, target.secretKey = "", ""
+	target.HasCredentials = req.SecretKey != ""
+	target.CreatedAt, target.UpdatedAt = now.Time, now.Time
+	c.JSON(http.StatusCreated, gin.H{"backup_target": target})
+}
+
+func (h *DatabaseHandler) UpdateBackupTarget(c *gin.Context) {
+	userID, ok := requireAuthenticatedUserID(c)
+	if !ok {
+		return
+	}
+	targetID := c.Param("id")
+	row, err := h.queries.GetBackupTargetByIDAndUser(c.Request.Context(), sqlcdb.GetBackupTargetByIDAndUserParams{ID: targetID, UserID: userID})
+	if err != nil {
+		c.JSON(http.StatusNotFound, gin.H{"error": "Backup target not found", "code": "NOT_FOUND"})
+		return
+	}
+	var req backupTargetRequest
+	if err := c.ShouldBindJSON(&req); err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error(), "code": "VALIDATION"})
+		return
+	}
+	if err := normalizeBackupTargetRequest(&req); err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error(), "code": "VALIDATION"})
+		return
+	}
+	useTLS := row.UseTls
+	if req.UseTLS != nil {
+		useTLS = *req.UseTLS
+	}
+	// Empty credentials keep the stored pair.
+	accessKey := row.AccessKey
+	secretKey := row.SecretKey
+	if req.AccessKey != "" || req.SecretKey != "" {
+		accessKey = secrets.Encrypt(req.AccessKey)
+		secretKey = secrets.Encrypt(req.SecretKey)
+	}
+
+	target := BackupTarget{
+		Endpoint:  req.Endpoint,
+		Bucket:    req.Bucket,
+		Region:    req.Region,
+		Prefix:    req.Prefix,
+		UseTLS:    useTLS,
+		accessKey: secrets.Decrypt(accessKey),
+		secretKey: secrets.Decrypt(secretKey),
+	}
+	probeCtx, cancel := context.WithTimeout(c.Request.Context(), 10*time.Second)
+	defer cancel()
+	if _, err := probeBackupTarget(probeCtx, target); err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": fmt.Sprintf("Connection check failed: %v", err), "code": "DEPENDENCY_UNAVAILABLE"})
+		return
+	}
+
+	if err := h.queries.UpdateBackupTargetByIDAndUser(c.Request.Context(), sqlcdb.UpdateBackupTargetByIDAndUserParams{
+		Name:      req.Name,
+		Endpoint:  req.Endpoint,
+		Bucket:    req.Bucket,
+		Region:    req.Region,
+		Prefix:    req.Prefix,
+		AccessKey: accessKey,
+		SecretKey: secretKey,
+		UseTls:    useTLS,
+		UpdatedAt: sql.NullTime{Time: time.Now(), Valid: true},
+		ID:        targetID,
+		UserID:    userID,
+	}); err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to update backup target"})
+		return
+	}
+	c.JSON(http.StatusOK, gin.H{"message": "Backup target updated"})
+}
+
+func (h *DatabaseHandler) DeleteBackupTarget(c *gin.Context) {
+	userID, ok := requireAuthenticatedUserID(c)
+	if !ok {
+		return
+	}
+	targetID := c.Param("id")
+	count, err := h.queries.CountDatabasesUsingBackupTarget(c.Request.Context(), sql.NullString{String: targetID, Valid: true})
+	if err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to check target usage"})
+		return
+	}
+	if count > 0 {
+		c.JSON(http.StatusConflict, gin.H{"error": fmt.Sprintf("%d database(s) still back up to this target", count), "code": "CONFLICT"})
+		return
+	}
+	if err := h.queries.DeleteBackupTargetByIDAndUser(c.Request.Context(), sqlcdb.DeleteBackupTargetByIDAndUserParams{ID: targetID, UserID: userID}); err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to delete backup target"})
+		return
+	}
+	LogAudit(userID, "backup_target", targetID, "delete", nil)
+	c.JSON(http.StatusOK, gin.H{"message": "Backup target deleted"})
+}
+
+func (h *DatabaseHandler) TestBackupTarget(c *gin.Context) {
+	userID, ok := requireAuthenticatedUserID(c)
+	if !ok {
+		return
+	}
+	targetID := c.Param("id")
+	row, err := h.queries.GetBackupTargetByIDAndUser(c.Request.Context(), sqlcdb.GetBackupTargetByIDAndUserParams{ID: targetID, UserID: userID})
+	if err != nil {
+		c.JSON(http.StatusNotFound, gin.H{"error": "Backup target not found", "code": "NOT_FOUND"})
+		return
+	}
+	target := mapBackupTargetRow(row)
+	probeCtx, cancel := context.WithTimeout(c.Request.Context(), 10*time.Second)
+	defer cancel()
+	latency, probeErr := probeBackupTarget(probeCtx, target)
+	if probeErr != nil {
+		c.JSON(http.StatusOK, gin.H{"ok": false, "error": probeErr.Error()})
+		return
+	}
+	c.JSON(http.StatusOK, gin.H{"ok": true, "latency_ms": latency.Milliseconds()})
+}
+
+// uploadBackupToTarget copies the archive out of the backup volume and puts
+// it in the configured S3 target. Returns the object key, or "" when no
+// target is configured.
+func (h *DatabaseHandler) uploadBackupToTarget(ctx context.Context, db sqlcdb.DatabaseService, archivePath, backupID string) (string, error) {
+	if !db.BackupTargetID.Valid || db.BackupTargetID.String == "" {
+		return "", nil
+	}
+	targetRow, err := h.queries.GetBackupTargetByID(ctx, db.BackupTargetID.String)
+	if err != nil {
+		return "", fmt.Errorf("backup target lookup failed: %w", err)
+	}
+	target := mapBackupTargetRow(targetRow)
+
+	archive, err := h.readBackupArchive(ctx, archivePath)
+	if err != nil {
+		return "", fmt.Errorf("read archive: %w", err)
+	}
+	defer func() {
+		_, _ = io.Copy(io.Discard, archive)
+		_ = archive.Close()
+	}()
+
+	client, err := target.s3Client()
+	if err != nil {
+		return "", err
+	}
+	key := target.Prefix
+	if key != "" {
+		key += "/"
+	}
+	key += "databases/" + db.ID + "/" + sanitizeBackupArchivePath(archivePath)
+	_, err = client.PutObject(ctx, target.Bucket, key, archive, -1, minio.PutObjectOptions{ContentType: "application/gzip"})
+	if err != nil {
+		return "", fmt.Errorf("s3 upload: %w", err)
+	}
+	_ = h.queries.SetDatabaseBackupRemoteKeyByID(ctx, sqlcdb.SetDatabaseBackupRemoteKeyByIDParams{
+		RemoteKey: sql.NullString{String: key, Valid: true},
+		ID:        backupID,
+	})
+	return key, nil
+}
+
+// readBackupArchive streams an archive out of the shared backup volume via a
+// stopped holder container — the volume has no direct host path.
+func (h *DatabaseHandler) readBackupArchive(ctx context.Context, archivePath string) (io.ReadCloser, error) {
+	holderID, err := h.createBackupVolumeHolder(ctx)
+	if err != nil {
+		return nil, err
+	}
+	reader, err := h.dockerClient.CopyFromContainer(ctx, holderID, "/backup/"+sanitizeBackupArchivePath(archivePath))
+	if err != nil {
+		_ = h.dockerClient.RemoveContainer(context.Background(), holderID, true)
+		return nil, err
+	}
+	// The holder must outlive the stream — deleting the source container while
+	// dockerd serves the archive stalls the read without an error.
+	return &archiveReader{tar: reader, cleanup: func() {
+		_ = h.dockerClient.RemoveContainer(context.Background(), holderID, true)
+	}}, nil
+}
+
+// downloadBackupToVolume fetches a remote archive back into the backup volume
+// so the normal restore path can run unchanged.
+func (h *DatabaseHandler) downloadBackupToVolume(ctx context.Context, db sqlcdb.DatabaseService, remoteKey, archivePath string) error {
+	targetRow, err := h.queries.GetBackupTargetByID(ctx, db.BackupTargetID.String)
+	if err != nil {
+		return fmt.Errorf("backup target lookup failed: %w", err)
+	}
+	target := mapBackupTargetRow(targetRow)
+	client, err := target.s3Client()
+	if err != nil {
+		return err
+	}
+	obj, err := client.GetObject(ctx, target.Bucket, remoteKey, minio.GetObjectOptions{})
+	if err != nil {
+		return err
+	}
+	defer obj.Close()
+
+	archive := sanitizeBackupArchivePath(archivePath)
+	if archive == "" {
+		return errors.New("backup path is required")
+	}
+
+	var buf bytes.Buffer
+	tw := tar.NewWriter(&buf)
+	data, err := io.ReadAll(obj)
+	if err != nil {
+		return fmt.Errorf("s3 download: %w", err)
+	}
+	if err := tw.WriteHeader(&tar.Header{Name: archive, Mode: 0o644, Size: int64(len(data))}); err != nil {
+		return err
+	}
+	if _, err := tw.Write(data); err != nil {
+		return err
+	}
+	if err := tw.Close(); err != nil {
+		return err
+	}
+
+	holderID, err := h.createBackupVolumeHolder(ctx)
+	if err != nil {
+		return err
+	}
+	defer func() { _ = h.dockerClient.RemoveContainer(context.Background(), holderID, true) }()
+	return h.dockerClient.CopyToContainer(ctx, holderID, "/backup", &buf)
+}
+
+// backupArchiveExists reports whether the archive is still in the local
+// backup volume — a copy attempt on a holder container is the cheapest check.
+func (h *DatabaseHandler) backupArchiveExists(ctx context.Context, archivePath string) (bool, error) {
+	holderID, err := h.createBackupVolumeHolder(ctx)
+	if err != nil {
+		return false, err
+	}
+	defer func() { _ = h.dockerClient.RemoveContainer(context.Background(), holderID, true) }()
+	reader, err := h.dockerClient.CopyFromContainer(ctx, holderID, "/backup/"+sanitizeBackupArchivePath(archivePath))
+	if err != nil {
+		return false, nil
+	}
+	_ = reader.Close()
+	return true, nil
+}
+
+// createBackupVolumeHolder creates a container mounting the backup volume so
+// archives can be copied in and out. It must be started — docker cp/archive
+// only resolves volume mounts on containers that have run at least once.
+func (h *DatabaseHandler) createBackupVolumeHolder(ctx context.Context) (string, error) {
+	if err := h.ensureImage(ctx, managedDatabaseBackupImage); err != nil {
+		return "", err
+	}
+	holderID, err := h.dockerClient.CreateContainer(ctx, docker.ContainerConfig{
+		Image:         managedDatabaseBackupImage,
+		Cmd:           []string{"true"},
+		RestartPolicy: "no",
+		Mounts:        []mount.Mount{{Type: mount.TypeVolume, Source: managedDatabaseBackupVolume, Target: "/backup"}},
+		Labels:        map[string]string{"containr.managed": "true", "containr.utility": "backup-io"},
+		NetworkMode:   "none",
+	})
+	if err != nil {
+		return "", err
+	}
+	if err := h.dockerClient.StartContainer(ctx, holderID); err != nil {
+		_ = h.dockerClient.RemoveContainer(context.Background(), holderID, true)
+		return "", fmt.Errorf("failed to start backup holder: %w", err)
+	}
+	return holderID, nil
+}
+
+// archiveReader unwraps the tar stream CopyFromContainer returns.
+type archiveReader struct {
+	tar     io.ReadCloser
+	tr      *tar.Reader
+	err     error
+	cleanup func()
+}
+
+func (r *archiveReader) Read(p []byte) (int, error) {
+	if r.err != nil {
+		return 0, r.err
+	}
+	if r.tr == nil {
+		r.tr = tar.NewReader(r.tar)
+		// Skip to the first regular file entry.
+		for {
+			hdr, err := r.tr.Next()
+			if err != nil {
+				r.err = err
+				return 0, err
+			}
+			if hdr.Typeflag == tar.TypeReg {
+				break
+			}
+		}
+	}
+	n, err := r.tr.Read(p)
+	if err != nil {
+		r.err = err
+	}
+	return n, err
+}
+
+func (r *archiveReader) Close() error {
+	err := r.tar.Close()
+	if r.cleanup != nil {
+		r.cleanup()
+		r.cleanup = nil
+	}
+	return err
+}

app/backend/internal/api/backuptargets_test.go

@@ -0,0 +1,60 @@
+package api
+
+import (
+	"archive/tar"
+	"bytes"
+	"io"
+	"testing"
+)
+
+func TestNormalizeBackupTargetRequest(t *testing.T) {
+	req := backupTargetRequest{
+		Name:     " garage ",
+		Endpoint: "https://garage.local:3900/",
+		Bucket:   " backups ",
+		Prefix:   " /prod/dbs/ ",
+	}
+	if err := normalizeBackupTargetRequest(&req); err != nil {
+		t.Fatalf("normalize failed: %v", err)
+	}
+	if req.Endpoint != "garage.local:3900" {
+		t.Fatalf("endpoint not normalized: %q", req.Endpoint)
+	}
+	if req.Bucket != "backups" || req.Prefix != "prod/dbs" {
+		t.Fatalf("bucket/prefix not trimmed: %q %q", req.Bucket, req.Prefix)
+	}
+
+	for i, bad := range []backupTargetRequest{
+		{Endpoint: "e", Bucket: "b"}, // no name
+		{Name: "n", Bucket: "b"},     // no endpoint
+		{Name: "n", Endpoint: "e"},   // no bucket
+	} {
+		if err := normalizeBackupTargetRequest(&bad); err == nil {
+			t.Fatalf("case %d: expected error", i)
+		}
+	}
+}
+
+func TestArchiveReaderUnwrapsTar(t *testing.T) {
+	var buf bytes.Buffer
+	tw := tar.NewWriter(&buf)
+	payload := []byte("backup-bytes")
+	if err := tw.WriteHeader(&tar.Header{Name: "b.tar.gz", Mode: 0o644, Size: int64(len(payload))}); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := tw.Write(payload); err != nil {
+		t.Fatal(err)
+	}
+	if err := tw.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	r := &archiveReader{tar: io.NopCloser(&buf)}
+	got, err := io.ReadAll(r)
+	if err != nil {
+		t.Fatalf("read: %v", err)
+	}
+	if !bytes.Equal(got, payload) {
+		t.Fatalf("payload mismatch: %q", got)
+	}
+}

app/backend/internal/api/databases.go

@@ -54,7 +54,8 @@ type DatabaseService struct {
 	NextBackupAt   *time.Time           `json:"next_backup_at,omitempty"`
 	Provider       string               `json:"provider"` // managed | external
 	PublicPort     bool                 `json:"public_port" db:"public_port"`
-	External       *DatabaseExternalRef `json:"external,omitempty"` // connection target for external DBs
+	BackupTargetID string               `json:"backup_target_id,omitempty"` // S3-compatible archive destination
+	External       *DatabaseExternalRef `json:"external,omitempty"`         // connection target for external DBs
 	CreatedAt      time.Time            `json:"created_at" db:"created_at"`
 	UpdatedAt      time.Time            `json:"updated_at" db:"updated_at"`
 	ConnectionURL  string               `json:"connection_url"`
@@ -106,6 +107,7 @@ type DatabaseBackup struct {
 	CreatedAt time.Time `json:"created_at"`
 	Size      string    `json:"size"`
 	Status    string    `json:"status"` // completed, failed, in_progress
+	Remote    bool      `json:"remote"` // archive also exists on the configured backup target
 }
 
 // DatabaseSettings represents database configuration
@@ -131,6 +133,7 @@ type DatabaseUpdateRequest struct {
 	Plan           string  `json:"plan,omitempty"`
 	BackupSchedule *string `json:"backup_schedule,omitempty"`
 	PublicPort     *bool   `json:"public_port,omitempty"`
+	BackupTargetID *string `json:"backup_target_id,omitempty"` // empty string clears
 }
 
 // DatabaseActionRequest represents a request to perform database actions
@@ -417,12 +420,12 @@ func (h *DatabaseHandler) UpdateDatabase(c *gin.Context) {
 	req.Name = strings.TrimSpace(req.Name)
 	req.Plan = strings.TrimSpace(req.Plan)
 
-	if req.Name == "" && req.Plan == "" && req.BackupSchedule == nil && req.PublicPort == nil {
+	if req.Name == "" && req.Plan == "" && req.BackupSchedule == nil && req.PublicPort == nil && req.BackupTargetID == nil {
 		c.JSON(http.StatusBadRequest, gin.H{"error": "No fields to update"})
 		return
 	}
 
-	if req.PublicPort != nil {
+	if req.PublicPort != nil || req.BackupTargetID != nil {
 		row, err := h.queries.GetDatabaseServiceByIDAndUser(c.Request.Context(), sqlcdb.GetDatabaseServiceByIDAndUserParams{
 			ID:     databaseID,
 			UserID: userID,
@@ -431,23 +434,47 @@ func (h *DatabaseHandler) UpdateDatabase(c *gin.Context) {
 			c.JSON(http.StatusNotFound, gin.H{"error": "Database not found", "code": "NOT_FOUND"})
 			return
 		}
-		if row.Provider == "external" {
-			c.JSON(http.StatusBadRequest, gin.H{"error": "public_port applies to managed databases — external databases are already reachable", "code": "VALIDATION"})
-			return
+		if req.PublicPort != nil {
+			if row.Provider == "external" {
+				c.JSON(http.StatusBadRequest, gin.H{"error": "public_port applies to managed databases — external databases are already reachable", "code": "VALIDATION"})
+				return
+			}
+			if err := h.queries.SetDatabaseServicePublicPortByIDAndUser(c.Request.Context(), sqlcdb.SetDatabaseServicePublicPortByIDAndUserParams{
+				PublicPort: *req.PublicPort,
+				UpdatedAt:  sql.NullTime{Time: time.Now(), Valid: true},
+				ID:         databaseID,
+				UserID:     userID,
+			}); err != nil {
+				c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to update public port"})
+				return
+			}
+			// Port bindings are baked into the container — recreate it so the
+			// new bind scope takes effect. The data volume survives.
+			if *req.PublicPort != row.PublicPort {
+				go h.reprovisionManagedDatabase(databaseID, row.Name, row.Type)
+			}
 		}
-		if err := h.queries.SetDatabaseServicePublicPortByIDAndUser(c.Request.Context(), sqlcdb.SetDatabaseServicePublicPortByIDAndUserParams{
-			PublicPort: *req.PublicPort,
-			UpdatedAt:  sql.NullTime{Time: time.Now(), Valid: true},
-			ID:         databaseID,
-			UserID:     userID,
-		}); err != nil {
-			c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to update public port"})
-			return
-		}
-		// Port bindings are baked into the container — recreate it so the
-		// new bind scope takes effect. The data volume survives.
-		if *req.PublicPort != row.PublicPort {
-			go h.reprovisionManagedDatabase(databaseID, row.Name, row.Type)
+		if req.BackupTargetID != nil {
+			if row.Provider == "external" {
+				c.JSON(http.StatusBadRequest, gin.H{"error": "backup targets apply to managed databases — external backups are not supported yet", "code": "VALIDATION"})
+				return
+			}
+			targetID := strings.TrimSpace(*req.BackupTargetID)
+			if targetID != "" {
+				if _, err := h.queries.GetBackupTargetByIDAndUser(c.Request.Context(), sqlcdb.GetBackupTargetByIDAndUserParams{ID: targetID, UserID: userID}); err != nil {
+					c.JSON(http.StatusNotFound, gin.H{"error": "Backup target not found", "code": "NOT_FOUND"})
+					return
+				}
+			}
+			if err := h.queries.SetDatabaseBackupTargetByIDAndUser(c.Request.Context(), sqlcdb.SetDatabaseBackupTargetByIDAndUserParams{
+				BackupTargetID: sql.NullString{String: targetID, Valid: targetID != ""},
+				UpdatedAt:      sql.NullTime{Time: time.Now(), Valid: true},
+				ID:             databaseID,
+				UserID:         userID,
+			}); err != nil {
+				c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to update backup target"})
+				return
+			}
 		}
 	}
 
@@ -991,6 +1018,7 @@ func (h *DatabaseHandler) resolveBackupConfig(ctx context.Context, userID string
 			CreatedAt: createdAt,
 			Size:      row.Size,
 			Status:    row.Status,
+			Remote:    row.RemoteKey.Valid && row.RemoteKey.String != "",
 		})
 		if lastBackup == nil && row.Status == "completed" {
 			t := createdAt
@@ -1144,6 +1172,7 @@ func mapDatabaseServiceRow(row sqlcdb.DatabaseService) DatabaseService {
 		NextBackupAt:   databaseNullTimePtr(row.NextBackupAt),
 		Provider:       row.Provider,
 		PublicPort:     row.PublicPort,
+		BackupTargetID: databaseNullString(row.BackupTargetID),
 		ConnectionURL:  databaseNullString(row.ConnectionUrl),
 		CreatedAt:      databaseNullTime(row.CreatedAt),
 		UpdatedAt:      databaseNullTime(row.UpdatedAt),
@@ -1815,10 +1844,17 @@ func (h *DatabaseHandler) createBackupProcess(databaseID, backupID, backupPath s
 		_ = h.setDatabaseBackupStatus(backupID, "failed", "0 B", false)
 		return
 	}
+	if dbRow, err := h.queries.GetDatabaseServiceByID(ctx, databaseID); err == nil {
+		if key, err := h.uploadBackupToTarget(ctx, dbRow, backupPath, backupID); err != nil {
+			log.Printf("containr: backup %s remote upload failed: %v (local archive kept)", backupID, err)
+		} else if key != "" {
+			log.Printf("containr: backup %s shipped to %s", backupID, key)
+		}
+	}
 	_ = h.setDatabaseBackupStatus(backupID, "completed", sizeLabel, true)
 }
 
-func (h *DatabaseHandler) restoreBackupProcess(databaseID, _ string, backupPath string) {
+func (h *DatabaseHandler) restoreBackupProcess(databaseID, backupID string, backupPath string) {
 	ctx, cancel := context.WithTimeout(context.Background(), 20*time.Minute)
 	defer cancel()
 
@@ -1827,6 +1863,22 @@ func (h *DatabaseHandler) restoreBackupProcess(databaseID, _ string, backupPath
 		return
 	}
 
+	// Restore the archive from the configured S3 target when the local copy
+	// is gone (fresh node, pruned volume) — local takes precedence.
+	if dbRow, err := h.queries.GetDatabaseServiceByID(ctx, databaseID); err == nil && dbRow.BackupTargetID.Valid && dbRow.BackupTargetID.String != "" {
+		if ok, _ := h.backupArchiveExists(ctx, backupPath); !ok {
+			if b, err := h.queries.GetDatabaseBackupByIDAndDatabaseAndUser(ctx, sqlcdb.GetDatabaseBackupByIDAndDatabaseAndUserParams{
+				ID: backupID, DatabaseID: databaseID, UserID: dbRow.UserID,
+			}); err == nil && b.RemoteKey.Valid && b.RemoteKey.String != "" {
+				if err := h.downloadBackupToVolume(ctx, dbRow, b.RemoteKey.String, backupPath); err != nil {
+					log.Printf("containr: remote restore fetch failed for backup %s: %v", backupID, err)
+					_ = h.setDatabaseStatus(databaseID, "error")
+					return
+				}
+			}
+		}
+	}
+
 	_ = h.setDatabaseStatus(databaseID, "building")
 	_ = h.stopManagedDatabase(databaseID)
 

app/backend/internal/api/routes.go

@@ -354,6 +354,13 @@ func SetupRoutes(router *gin.Engine, db *database.DB, redis *database.Redis, cfg
 			// One-off exec console (docker exec, 30s ceiling)
 			authed.POST("/services/:id/exec", handleExecInService)
 
+			// S3-compatible backup targets — owner-scoped, keys encrypted at rest.
+			authed.GET("/backup-targets", databaseHandler.ListBackupTargets)
+			authed.POST("/backup-targets", databaseHandler.CreateBackupTarget)
+			authed.PUT("/backup-targets/:id", databaseHandler.UpdateBackupTarget)
+			authed.DELETE("/backup-targets/:id", databaseHandler.DeleteBackupTarget)
+			authed.POST("/backup-targets/:id/test", databaseHandler.TestBackupTarget)
+
 			// Private-image registries — owner-scoped, credentials encrypted at rest.
 			authed.GET("/registries", handleListRegistries)
 			authed.POST("/registries", handleCreateRegistry)