Sync & Data Management

FuelFlow uses a sophisticated dual-sync system to keep your data synchronized across your iPhone and Apple Watch. This guide explains how it works, what happens in different scenarios, and how to manage your data.

The Dual-Sync Architecture

FuelFlow uses two independent sync methods that work together seamlessly:

1. Instant Local Sync (Primary)

Technology: WatchConnectivity framework (Apple’s native iPhone-Watch communication)

Speed: Less than 1 second

Connection: Bluetooth or WiFi Direct

Internet required: No

Range: Typical Bluetooth range (about 10 meters / 30 feet)

When it works:

  • Both devices are powered on
  • Bluetooth is enabled on both devices
  • Devices are within range
  • Apps are installed on both devices

What syncs:

  • Starting a new session
  • Ending a session
  • Logging food
  • Logging water
  • Session updates
  • Library changes

2. CloudKit Sync (Backup)

Technology: Apple’s CloudKit framework

Speed: 2-10 seconds (varies with network)

Connection: Internet (WiFi or Cellular)

Internet required: Yes

Range: Unlimited (anywhere with internet)

When it works:

  • Device has internet connection
  • Signed into iCloud
  • iCloud Drive enabled

What syncs:

  • All sessions
  • Complete food library
  • Settings and preferences
  • Historical data

How the Dual-Sync System Works

The beauty of FuelFlow’s sync is that you don’t have to think about it. The app intelligently chooses the best method:

Scenario 1: Devices Together (Most Common)

Situation: You’re out for a run with your Apple Watch. Your iPhone is in your pocket or armband.

What happens:

  1. You log a gel on your Apple Watch
  2. Instant sync sends data to iPhone via Bluetooth
  3. iPhone receives data in < 1 second
  4. iPhone display updates immediately
  5. CloudKit syncs in background (backup)

Why it’s great: Instant feedback, works offline (airplane mode + Bluetooth), no internet data used.

Scenario 2: Devices Apart

Situation: You’re on a run with just your Apple Watch. iPhone is at home.

What happens:

  1. You log nutrition on your Watch
  2. Data is saved locally on Watch
  3. When you get home and Watch reconnects to iPhone:
    • Instant sync transfers data immediately
    • Or CloudKit sync transfers when Watch gets WiFi
  4. iPhone updates with all your logs

Why it’s great: Never lose data, syncs automatically when devices reunite.

Scenario 3: Offline Everywhere

Situation: You’re in an area with no internet and devices are apart.

What happens:

  1. Each device stores data locally
  2. When either device gets internet:
    • CloudKit sync synchronizes all changes
  3. When devices reconnect:
    • Instant sync ensures perfect synchronization

Why it’s great: Keep logging even without connectivity. Everything syncs when possible.

Scenario 4: Cellular Apple Watch

Situation: You have cellular Apple Watch and left iPhone at home.

What happens:

  1. You log nutrition on Watch during your run
  2. Watch uses cellular to sync via CloudKit
  3. iPhone at home receives CloudKit sync
  4. Data appears on iPhone automatically

Why it’s great: Complete independence while still staying in sync.

What Data Is Synchronized

Always Synced

Sessions:

  • All active and past sessions
  • Session start/end times
  • Activity types
  • Nutrition goals
  • All logs (food and water)
  • Timestamps

Food Library:

  • All food items
  • Names, carbs, sodium
  • Categories
  • Custom entries

Settings:

  • Notification preferences
  • Units (metric/imperial)
  • Display preferences

Device-Specific (Not Synced)

iPhone:

  • Lock Screen Live Activity state
  • App-specific UI state
  • Notification badges

Apple Watch:

  • Watch complication settings
  • Watch face configurations
  • Haptic feedback preferences

Understanding Sync Status

Status Indicators

iPhone:

  • Green checkmark (✓): All data synced successfully
  • Syncing (↻): Sync in progress
  • Cloud (☁): CloudKit sync active
  • Warning (⚠): Sync issue (see troubleshooting)

Apple Watch:

  • Checkmark (✓): Synced with iPhone
  • Syncing (↻): Sync in progress
  • Cloud (☁): Using CloudKit

Where to Check Sync Status

iPhone:

  • Settings tab → iCloud Sync status
  • Pull down on any screen to see sync indicator

Apple Watch:

  • Force touch on main screen
  • Check sync status

Data Privacy & Security

End-to-End Encryption

All data synced via CloudKit is end-to-end encrypted:

  • Apple cannot read your data
  • Data is encrypted on device before upload
  • Only your devices can decrypt the data
  • Secure in transit and at rest

Local Sync Security

Instant sync via Bluetooth:

  • Uses Apple’s WatchConnectivity framework
  • Encrypted by iOS/watchOS automatically
  • Requires devices to be paired (secure pairing process)
  • Data never leaves your personal device network

What Data Does FuelFlow Store?

On Apple’s Servers (CloudKit):

  • Your sessions (encrypted)
  • Your food library (encrypted)
  • Your settings (encrypted)

Not stored anywhere:

  • No account information (uses iCloud)
  • No personal data beyond what you enter
  • No tracking or analytics data
  • No sharing with third parties

Data Ownership

You own all your data:

  • Export anytime (Settings → Export Data)
  • Delete anytime (Settings → Delete All Data)
  • Data deleted from CloudKit when you delete locally

Managing Your Data

Exporting Data

Why export?

  • Backup your sessions
  • Share with coaches
  • Analyze in spreadsheets
  • Archive for long-term records

How to export:

  1. Open FuelFlow on iPhone
  2. Go to Settings tab
  3. Tap Export Data
  4. Choose format:
    • CSV - Spreadsheet compatible
    • JSON - Raw data format
  5. Select date range:
    • Last 30 days
    • Last 90 days
    • All time
    • Custom range
  6. Tap Export
  7. Share via:
    • Email
    • Files app
    • iCloud Drive
    • AirDrop

What’s included:

  • All sessions in selected range
  • Complete nutrition logs
  • Timestamps and duration
  • Calculated statistics

Deleting Data

Delete individual sessions:

  1. History tab
  2. Swipe left on session
  3. Tap Delete
  4. Confirm

Delete all data:

  1. Settings tab
  2. Delete All Data (at bottom)
  3. Enter confirmation
  4. All data removed from device and CloudKit

Note: Deletions sync across devices. This is permanent.

Storage Usage

iCloud Storage:

  • Typical usage: 1-10 MB
  • Even with years of data: < 50 MB
  • Very minimal impact on iCloud storage

Device Storage:

  • iPhone: 10-20 MB (app + data)
  • Apple Watch: 5-10 MB

Troubleshooting Sync Issues

“Data not syncing between devices”

Check 1: Bluetooth (for Instant Sync)

  • Settings → Bluetooth → On (both devices)
  • Bring devices close together
  • Restart Bluetooth if needed

Check 2: iCloud (for CloudKit Sync)

  • Settings → [Your Name] → iCloud
  • Ensure iCloud Drive is ON
  • Check available iCloud storage
  • Ensure FuelFlow has iCloud permission

Check 3: Internet Connection

  • CloudKit requires internet
  • WiFi or cellular data
  • Check connection speed

Check 4: App Versions

  • Ensure both devices have latest FuelFlow version
  • Update from App Store if needed

“Sync stuck at ‘Syncing…’”

Fixes:

  1. Force quit FuelFlow on both devices
  2. Reopen the app
  3. Wait 30 seconds for sync to complete
  4. If still stuck, check internet connection
  5. Try toggling Airplane mode on/off

“Session started on iPhone not appearing on Watch”

Immediate fix:

  1. Open FuelFlow on Apple Watch
  2. Pull down to refresh
  3. Session should appear

If not working:

  1. Check Bluetooth is enabled
  2. Force quit and reopen Watch app
  3. Wait for CloudKit sync (few seconds with internet)

“Duplicate sessions appearing”

Rare but possible causes:

  • Editing same session on both devices simultaneously
  • Sync conflict during poor connectivity

Fix:

  1. Keep the correct session
  2. Delete the duplicate
  3. Deletion syncs to other device

Prevention: Avoid editing same session on both devices at same time

“Lost data after device died”

Don’t worry:

  • Data is saved locally even without sync
  • When device charges and turns on:
    • CloudKit syncs automatically
    • All data recovers
  • May take a few minutes to fully sync

“Changed food item, changes not syncing”

Expected behavior:

  • Changes to food items sync via CloudKit
  • May take 5-10 seconds
  • Pull down to refresh if needed

If not syncing:

  1. Check iCloud connection
  2. Wait 30 seconds
  3. Force quit and reopen app

Sync in Different Scenarios

Airplane Mode

Bluetooth ON, WiFi OFF, Cellular OFF:

  • ✅ Instant local sync works
  • ❌ CloudKit sync not available
  • Data syncs when airplane mode disabled

Use case: Flying to a race, tracking nutrition on plane

Ultra-Distance Events

Long events with spotty connectivity:

  • Both devices store data locally
  • Instant sync when devices reconnect
  • CloudKit syncs when internet available
  • No data loss regardless of connectivity

International Travel

Cellular data disabled, WiFi only:

  • Instant sync via Bluetooth always works
  • CloudKit syncs when connected to WiFi
  • Use airplane mode + Bluetooth to preserve battery

Device Upgrade

Getting new iPhone or Apple Watch:

  1. Sign into iCloud on new device
  2. Install FuelFlow
  3. CloudKit automatically syncs all data
  4. Complete history and library restored

Using Multiple Devices

Example: iPhone, iPad, Apple Watch:

  • All devices sync via CloudKit
  • Instant sync works between iPhone and Watch
  • iPad syncs via CloudKit only
  • All devices stay synchronized

Advanced Data Topics

Conflict Resolution

What happens if you edit same session on both devices?

  • FuelFlow uses “last write wins”
  • Most recent change is kept
  • Very rare in practice (sessions typically edited on one device)

Sync Frequency

Instant Sync:

  • Happens immediately when you make a change
  • < 1 second latency
  • Event-driven (not polling)

CloudKit Sync:

  • Automatic background sync
  • Triggered by changes
  • Also syncs every few minutes as backup
  • Efficient - only syncs changes

Offline Queueing

Multiple changes while offline:

  • All changes queued locally
  • When connectivity restored:
    • All changes sync in order
    • Maintains correct timestamps
    • Preserves data integrity

Best Practices

For Reliable Sync

  1. Keep Bluetooth enabled - Allows instant sync
  2. Stay signed into iCloud - Ensures CloudKit backup
  3. Keep apps updated - Latest sync improvements
  4. Charge devices - Low battery can pause background sync
  5. Don’t force quit - Let apps sync in background

For Long Events

  1. Start with full battery - Both devices
  2. Enable airplane mode + Bluetooth - Saves battery, keeps instant sync
  3. Trust the sync - Don’t worry about connectivity during event
  4. Review after finish - All data will be synchronized

For Data Safety

  1. Regular exports - Backup important sessions
  2. Keep iCloud enabled - Automatic cloud backup
  3. Don’t delete iCloud data - Unless you’re sure
  4. Update devices - Latest sync reliability improvements

Need Help?

Email: support@fuelflow.run Website: fuelflow.run

Your data is always safe, always synchronized, and always accessible. FuelFlow’s dual-sync system ensures you never lose a single nutrition log, no matter what happens.