EVENTSTORE
An EventStore in DeQL declares the append‑only storage and operational characteristics for events. It is the only infrastructure‑level Block in the language — everything else expresses pure domain logic.
Syntax
Section titled “Syntax”CREATE EVENTSTORE <Name>WITH ( <key> = <value>, ...);The WITH block is a flat key-value configuration organized into logical sections. All sections are optional except durable.* — you need at least one durable store.
Minimal Example
Section titled “Minimal Example”The smoke test uses a minimal local-dev store with just the essentials:
CREATE EVENTSTORE local_dev WITH ( envelope.event_id_key = 'event_id', durable.type = 'parquet', durable.path = '/tmp/deql/', strict.immutable_events = true);This is the simplest valid eventstore — an event ID key, a durable Parquet store, and immutability enforcement.
Local Development Example
Section titled “Local Development Example”A slightly more complete local-dev store:
CREATE EVENTSTORE local_devWITH ( envelope.event_id_key = 'event_id', envelope.stream_type_key = 'stream_type', envelope.stream_id_key = 'stream_id', envelope.seq_key = 'seq', envelope.event_type_key = 'event_type', envelope.occurred_at_key = 'occurred_at', envelope.payload_key = 'data',
id.event_id.format = 'uuidv7',
ordering.per_stream = 'seq',
durable.type = 'parquet', durable.path = 'file:///tmp/deql/events/', durable.compression = 'snappy',
partition.by = ('dt','stream_type'), partition.dt.expr = 'DATE(occurred_at)',
strict.immutable_events = true);Full Reference Example
Section titled “Full Reference Example”CREATE EVENTSTORE telecom_defaultWITH ( -- ============================================================ -- 1) EVENT ENVELOPE / IDENTITY DEFAULTS -- ============================================================ envelope.event_id_key = 'event_id', envelope.stream_type_key = 'stream_type', envelope.stream_id_key = 'stream_id', envelope.seq_key = 'seq', envelope.event_type_key = 'event_type', envelope.event_version_key = 'event_version', envelope.occurred_at_key = 'occurred_at', envelope.ingested_at_key = 'ingested_at', envelope.payload_key = 'data', envelope.metadata_key = 'metadata', envelope.command_id_key = 'command_id', envelope.correlation_id_key = 'correlation_id', envelope.causation_id_key = 'causation_id', envelope.tenant_id_key = 'tenant_id',
-- Event ID strategy (recommend uuidv7 for time locality) id.event_id.format = 'uuidv7', id.command_id.required = true, id.command_id.unique_scope = 'stream', id.correlation_id.optional = true,
-- Ordering rules (correctness) ordering.per_stream = 'seq', ordering.global = ('ingested_at','event_id'),
-- ============================================================ -- 2) DURABLE EVENT STORE (MANDATORY): PARQUET -- ============================================================ durable.type = 'parquet', durable.path = 's3://deql/events/', durable.file_pattern = 'dt={dt}/stream_type={stream_type}/part-{writer}-{file_seq}.parquet', durable.commit.protocol = 'atomic_rename', durable.commit.manifest_path = 's3://deql/events/_manifests/', durable.compression = 'zstd', durable.compression.level = 3, durable.dictionary.enabled = true,
-- ============================================================ -- 3) PARTITIONING (HIGHLY RECOMMENDED) -- ============================================================ partition.by = ('dt','stream_type'), partition.dt.expr = 'DATE(occurred_at)', partition.stream_type.expr = 'stream_type', partition.tenant_id.expr = 'tenant_id', partition.dt.granularity = 'day', partition.enforce = true,
-- ============================================================ -- 4) ROW GROUPS, SORTING, AND STATISTICS (PERFORMANCE) -- ============================================================ row_group.target_mb = 128, row_group.max_rows = 1_000_000, row_group.sort_by = ('stream_id','seq'), row_group.sort_order = 'asc', stats.enabled = true, stats.columns = ('stream_id','seq','event_type','occurred_at'), bloom.enabled = true, bloom.columns = ('stream_id','event_id'), bloom.fpp = 0.01,
-- ============================================================ -- 5) HOT TIERS (OPTIONAL): IN-MEM + WAL -- ============================================================ inmemory.enabled = true, inmemory.max_mb = 512, inmemory.ttl_seconds = 60, inmemory.index_by = ('stream_type','stream_id'),
wal.enabled = true, wal.path = 'file:///var/lib/deql/wal/', wal.segment_pattern = 'events-{yyyy}{MM}{dd}-{HH}-{segment}.wal', wal.rollover = 'size', wal.rollover_mb = 256, wal.fsync = true, wal.checksum = 'crc32c', wal.retention_hours = 24,
-- ============================================================ -- 6) COMPACTION / INGESTION PIPELINE (WAL → DURABLE) -- ============================================================ compaction.enabled = true, compaction.trigger = ('size_mb','time'), compaction.min_segment_mb = 64, compaction.max_file_mb = 512, compaction.target_file_mb = 256, compaction.max_open_files = 32, compaction.schedule = '*/5 * * * *',
-- ============================================================ -- 7) READ MERGE SEMANTICS (MULTI-TIER UNION) -- ============================================================ read.tiers = ('inmemory','wal','durable'), read.merge.strategy = 'union_dedupe_sort', read.dedupe.key = ('stream_type','stream_id','seq'), read.require_monotonic_seq = true, read.missing_seq.policy = 'error', read.default_order = ('stream_id','seq'),
-- ============================================================ -- 8) RETENTION / LIFECYCLE (OPTIONAL) -- ============================================================ retention.enabled = true, retention.durable_days = 3650, retention.wal_hours = 24, retention.inmemory_seconds = 60, retention.delete_mode = 'tombstone',
-- ============================================================ -- 9) SECURITY / ENCRYPTION (OPTIONAL HOOKS) -- ============================================================ security.encrypt.at_rest = true, security.kms.provider = 'aws_kms', security.kms.key_id = 'alias/deql-events', security.encrypt.in_transit = true,
-- ============================================================ -- 10) PROJECTION HOOKS (RUNTIME POLICY) -- ============================================================ projection.notify_on_commit = true, projection.notify_on_inspect = false, projection.mode = 'async',
-- ============================================================ -- 11) VALIDATION / STRICTNESS -- ============================================================ strict.immutable_events = true, strict.stream_type_enforced = true, strict.event_version_required= true, strict.tenant_required = false);Configuration Sections
Section titled “Configuration Sections”| Section | Required | Purpose |
|---|---|---|
envelope.* | Yes | Names of the standard event envelope fields used by the runtime |
id.* | Yes | Event ID format, command ID uniqueness, correlation/causation |
ordering.* | Yes | Per-stream and global ordering rules for replay correctness |
durable.* | Yes | Durable storage path, file pattern, commit protocol, compression |
partition.* | Recommended | Partition columns, expressions, granularity, enforcement |
row_group.* | Recommended | Row group sizing, sort order, statistics, bloom filters |
inmemory.* | Optional | In-memory hot tier for instant read-after-write |
wal.* | Optional | Write-ahead log for burst absorption before durable commit |
compaction.* | Optional | WAL → durable ingestion pipeline scheduling |
read.* | Optional | Multi-tier read merge strategy and deduplication |
retention.* | Optional | Lifecycle rules for durable, WAL, and in-memory tiers |
security.* | Optional | At-rest and in-transit encryption via KMS |
projection.* | Optional | Projection notification policy on commit and inspect |
strict.* | Optional | Immutability enforcement, stream type isolation, versioning |
Storage Tiers
Section titled “Storage Tiers”┌──────────────┐ ┌──────────────┐ ┌──────────────────────┐│ In-Memory │────▶│ WAL │────▶│ Durable Store ││ (hot, ~60s) │ │ (burst, ~24h)│ │ (permanent, years) │└──────────────┘ └──────────────┘ └──────────────────────┘ ▲ ▲ ▲ │ │ │ instant R/W fsync'd append columnar, compressed index by stream segment rollover partitioned + sortedReads merge across all tiers using read.merge.strategy = 'union_dedupe_sort', deduplicating by (stream_type, stream_id, seq) so the same event is never seen twice regardless of which tier it currently lives in.
Durable Event Store
Section titled “Durable Event Store”Events are stored as append-only files in the configured durable format (e.g., parquet, or any columnar format an implementation supports):
- Immutable — no UPDATE, no DELETE, no mutation
- Columnar — efficient compression and predicate pushdown
- Partitioned — by date and stream type for fast scans
- Sorted within row groups — by
(stream_id, seq)for optimal aggregate rehydration - Bloom-filtered — for point lookups on
stream_idandevent_id - Analytics-ready — the same files can be queried by any compatible analytics engine