Database Schema

SkySend uses SQLite with Drizzle ORM. The database file is located at data/skysend.db.

SQLite Configuration

PRAGMA journal_mode = WAL;        -- Concurrent reads + serialized writes
PRAGMA busy_timeout = 5000;       -- Wait up to 5s on lock contention
PRAGMA synchronous = NORMAL;      -- Safe with WAL, better write performance
PRAGMA foreign_keys = ON;         -- Enforce referential integrity

WAL (Write-Ahead Logging) mode allows concurrent reads while writes are serialized. This is more than sufficient for a single-instance self-hosted service.

Tables

uploads

Column	Type	Default	Description
id	TEXT (PK)	-	UUID v4
ownerToken	TEXT NOT NULL	-	Base64url-encoded owner token
authToken	TEXT NOT NULL	-	Base64url-encoded auth token
salt	BLOB NOT NULL	-	HKDF salt (16 bytes)
encryptedMeta	BLOB	NULL	AES-256-GCM encrypted metadata
nonce	BLOB	NULL	Metadata IV (12 bytes)
size	INTEGER NOT NULL	-	Total payload size in bytes
fileCount	INTEGER	1	Number of files (1 = single, >1 = archive)
hasPassword	INTEGER	0	Whether password protection is active
passwordSalt	BLOB	NULL	Password KDF salt (16 bytes)
passwordAlgo	TEXT	NULL	"argon2id" or "pbkdf2"
maxDownloads	INTEGER NOT NULL	-	Maximum allowed downloads
downloadCount	INTEGER	0	Current download count
expiresAt	TIMESTAMP NOT NULL	-	Expiry timestamp (Unix epoch)
createdAt	TIMESTAMP	current_unix_time	Creation timestamp
storagePath	TEXT NOT NULL	-	Filename on disk (UUID.bin)

Indexes

Index	Column	Purpose
idx_uploads_expires_at	expiresAt	Efficient cleanup queries

Concurrency

Download count updates (downloadCount = downloadCount + 1) are atomic SQL operations that hold the write lock for microseconds. WAL mode allows thousands of such writes per second while reads are never blocked.

The download route uses an atomic SQL update with a WHERE condition to prevent race conditions:

UPDATE uploads
SET downloadCount = downloadCount + 1
WHERE id = ? AND downloadCount < maxDownloads

If maxDownloads is already reached, the update affects zero rows and the request is rejected.

Migrations

Database migrations are managed by Drizzle ORM and stored in apps/server/src/db/migrations/. Migrations run automatically on server startup.