YantrikDB — A Cognitive Memory Engine for Persistent AI Systems

The memory engine for AI that actually knows you.

Get Started in 60 Seconds

For AI agents (MCP — works with Claude, Cursor, Windsurf, Copilot)

pip install yantrikdb-mcp

Add to your MCP client config:

{
  "mcpServers": {
    "yantrikdb": {
      "command": "yantrikdb-mcp"
    }
  }
}

That's it. The agent auto-recalls context, auto-remembers decisions, and auto-detects contradictions — no prompting needed. See yantrikdb-mcp for full docs.

As a Python library

The engine ships a default embedder (potion-base-2M, ~7 MB, distilled from BGE-base-en-v1.5) — record_text() / recall_text() work out of the box. No sentence-transformers install. No first-run model download. No ONNX runtime. Just one pip install.

import yantrikdb

# Default: bundled embedder, dim=64. Just works.
db = yantrikdb.YantrikDB.with_default("memory.db")

db.record("Alice is the engineering lead", importance=0.8, domain="people")
db.record("Project deadline is March 30", importance=0.9, domain="work")
db.record("User prefers dark mode", importance=0.6, domain="preference")

results = db.recall("who leads the team?", top_k=3)
# → [{"text": "Alice is the engineering lead", "score": 1.0}, ...]

db.relate("Alice", "Engineering", "leads")
db.get_edges("Alice")

db.think()  # consolidate, detect conflicts, mine patterns

db.close()

Want higher-quality embeddings?

Three opt-in upgrade paths, in increasing weight:

# 1. Larger bundled variant — downloads on first call, caches under
#    your user data dir. Self-hosted from yantrikos/yantrikdb-models;
#    no HuggingFace dependency, no rate limits.
db = yantrikdb.YantrikDB("memory.db", embedding_dim=256)
db.set_embedder_named("potion-base-8M")   # ~28 MB, ~92% MiniLM
# or:  db.set_embedder_named("potion-base-32M")  # ~121 MB, ~95% MiniLM

# 2. Bring your own embedder (sentence-transformers, fastembed, custom).
from sentence_transformers import SentenceTransformer
db = yantrikdb.YantrikDB("memory.db", embedding_dim=384)
db.set_embedder(SentenceTransformer("all-MiniLM-L6-v2"))

# 3. Slim build (no bundled embedder, must set_embedder yourself).
#    For deployments where the ~7 MB bundle is intolerable.
#    Rust:  yantrikdb = { version = "0.7", default-features = false }

As a Rust crate

[dependencies]
yantrikdb = "0.7"

# Want set_embedder_named() for runtime model upgrades?
# yantrikdb = { version = "0.7", features = ["embedder-download"] }

# Slim build (no bundled embedder, no network code path):
# yantrikdb = { version = "0.7", default-features = false }

The Problem

Current AI memory is:

Store everything → Embed → Retrieve top-k → Inject into context → Hope it helps.

That's not memory. That's a search engine with extra steps.

Real memory is hierarchical, compressed, contextual, self-updating, emotionally weighted, time-aware, and predictive. YantrikDB is built for that.

Why Not Existing Solutions?

Benchmark: Selective Recall vs. File-Based Memory

At 500 memories, file-based exceeds 32K context windows. At 5,000, it doesn't fit in any context window — not even 200K. YantrikDB stays at ~70 tokens per query. Precision improves with more data — the opposite of context stuffing.

Architecture

Design Principles

• Embedded, not client-server — single file, no server process (like SQLite)
• Local-first, sync-native — works offline, syncs when connected
• Cognitive operations, not SQL — record(), recall(), relate(), not SELECT
• Living system, not passive store — does work between conversations
• Thread-safe — Send + Sync with internal Mutex/RwLock, safe for concurrent access

Five Indexes, One Engine

┌──────────────────────────────────────────────────────┐
│                   YantrikDB Engine                    │
│                                                      │
│  ┌──────────┬──────────┬──────────┬──────────┐       │
│  │  Vector  │  Graph   │ Temporal │  Decay   │       │
│  │  (HNSW)  │(Entities)│ (Events) │  (Heap)  │       │
│  └──────────┴──────────┴──────────┴──────────┘       │
│  ┌──────────┐                                        │
│  │ Key-Value│  WAL + Replication Log (CRDT)          │
│  └──────────┘                                        │
└──────────────────────────────────────────────────────┘

1. Vector Index (HNSW) — semantic similarity search across memories
2. Graph Index — entity relationships, profile aggregation, bridge detection
3. Temporal Index — time-aware queries ("what happened Tuesday", "upcoming deadlines")
4. Decay Heap — importance scores that degrade over time, like human memory
5. Key-Value Store — fast facts, session state, scoring weights

Decoupled Write Path (v0.6.6+)

The vector index is structured as a two-tier LSM: a small mutable delta and an immutable HNSW cold tier swapped atomically via ArcSwap. Foreground writes only touch the delta (brief lock, O(1) push); HNSW work amortizes on a dedicated compactor thread. This is what eliminated the production wedge where sustained writes starved readers — see CONCURRENCY.md and docs/decoupled_write_path_rfc.md.

flowchart LR
    subgraph CLIENT["Caller"]
        C1["record / record_with_rid"]
        C2["recall / recall_with_seq"]
    end

    subgraph FG["Foreground — P1, brief locks only"]
        F1["assign_seq<br/>vec_seq.fetch_add<br/>(or fetch_max for cluster seq)"]
        F2["DeltaIndex.append<br/>brief RwLock&lt;Vec&gt; push"]
        F3["bump_visible_seq<br/>DashMap + AtomicU64<br/>(lock-free)"]
        F4["log_op → SQLite WAL"]
    end

    subgraph IDX["DeltaIndex (per engine)"]
        D1[("delta<br/>RwLock&lt;Vec&lt;DeltaEntry&gt;&gt;<br/>cap = delta_max (256)")]
        D2[("cold<br/>ArcSwap&lt;HnswIndex&gt;<br/>lock-free read")]
    end

    subgraph BG["Background — P3, dedicated threads"]
        B1["Compactor (1s tick)<br/>fires when delta past half-cap<br/>OR oldest entry > max_dirty_age"]
        B2["Materializer pool<br/>N = cores / 2<br/>drains pending oplog ops"]
    end

    subgraph STORE["SQLite (WAL mode, single file)"]
        S1["memories"]
        S2["oplog"]
        S3["entity_edges, sessions, ..."]
    end

    C1 --> F1
    F1 --> F2
    F2 --> D1
    F1 --> F3
    F1 --> F4
    F4 --> S2

    C2 -.->|"optional<br/>wait_for_visible_seq"| F3
    C2 --> D1
    C2 --> D2

    B1 -->|"seal + clone + ArcSwap.store"| D1
    B1 --> D2
    B2 --> S2
    B2 --> S1
    B2 --> S3

The structural invariant. Foreground (P1) and background (P3) do not share a lock primitive that holds for non-O(1) work. The cold tier is read lock-free via ArcSwap; the delta's RwLock is held for the O(1) push only. This is what makes "no single background task can wedge reads, writes, or recovery" enforceable — see CONCURRENCY.md Rules 2 and 3 for the names and failure modes if violated.

Cluster Mode (RFC 010 + Phase 6 RYW)

For multi-node deployments, yantrikdb-server wraps the engine with openraft for leader-elected replication. The four cluster-mutation primitives take the openraft commit-log index as their seq, so all nodes agree on a single global monotonic sequence — read-your-writes works across the cluster, not just within a node.

flowchart LR
    L["Leader<br/>HTTP request"]
    LR["Leader engine<br/>record_with_rid(seq=Some(log_idx))"]
    OR["openraft<br/>commit log"]
    F1["Follower 1 applier<br/>record_with_rid(seq=Some(log_idx))"]
    F2["Follower 2 applier<br/>record_with_rid(seq=Some(log_idx))"]
    R["Reader on any node<br/>recall_with_seq(min_seq=log_idx)"]

    L --> LR
    LR --> OR
    OR -->|replicate + apply| F1
    OR -->|replicate + apply| F2
    F1 -.->|"visible_seq[ns] reaches log_idx"| R
    F2 -.->|"visible_seq[ns] reaches log_idx"| R
    LR -.->|"visible_seq[ns] reaches log_idx"| R

Each record_with_rid / tombstone_with_rid / upsert_entity_edge_with_id / delete_entity_edge_with_id accepts an optional seq: Option<u64>. Single-node callers pass None and the engine allocates; cluster appliers pass Some(commit_log_index) and the engine ratchets vec_seq up to at least that value via fetch_max. After apply, visible_seq[namespace] reaches the log index, so any subsequent recall_with_seq(min_seq=N) blocks just long enough for the local node to have applied through index N — and no longer.

Memory Types (Tulving's Taxonomy)

All memories carry importance, valence (emotional tone), domain, source, certainty, and timestamps — used in a multi-signal scoring function that goes far beyond cosine similarity.

Key Capabilities

Relevance-Conditioned Scoring

Not just vector similarity. Every recall combines:

• Semantic similarity (HNSW) — what's topically related
• Temporal decay — recent memories score higher
• Importance weighting — critical decisions beat trivia
• Graph proximity — entity relationships boost connected memories
• Retrieval feedback — learns from past recall quality

Weights are tuned automatically from usage patterns.

Conflict Detection & Resolution

When memories contradict, YantrikDB doesn't guess — it creates a conflict segment:

"works at Google" (recorded Jan 15) vs. "works at Meta" (recorded Mar 1)
→ Conflict: identity_fact, priority: high, strategy: ask_user

Resolution is conversational: the AI asks naturally, not programmatically.

Semantic Consolidation

After many conversations, memories pile up. think() runs:

1. Consolidation — merge similar memories, extract patterns
2. Conflict scan — find contradictions across the knowledge base
3. Pattern mining — cross-domain discovery ("work stress correlates with health entries")
4. Trigger evaluation — proactive insights worth surfacing

Proactive Triggers

The engine generates triggers when it detects something worth reaching out about:

• Memory conflicts needing resolution
• Approaching deadlines (temporal awareness)
• Patterns detected across domains
• High-importance memories about to decay
• Goal tracking ("how's the marathon training?")

Every trigger is grounded in real memory data — not engagement farming.

Multi-Device Sync (CRDT)

Local-first with append-only replication log:

• CRDT merging — graph edges, memories, and metadata merge without conflicts
• Vector indexes rebuild locally — raw memories sync, each device rebuilds HNSW
• Forget propagation — tombstones ensure forgotten memories stay forgotten
• Conflict detection — contradictions across devices are flagged for resolution

Sessions & Temporal Awareness

sid = db.session_start("default", "claude-code")
db.record("decided to use PostgreSQL")  # auto-linked to session
db.record("Alice suggested Redis for caching")
db.session_end(sid)
# → computes: memory_count, avg_valence, topics, duration

db.stale(days=14)    # high-importance memories not accessed recently
db.upcoming(days=7)  # memories with approaching deadlines

Full API

Technical Decisions

Ecosystem

Roadmap

• V0 — Embedded engine, core memory model (record, recall, relate, consolidate, decay)
• V1 — Replication log, CRDT-based sync between devices
• V2 — Conflict resolution with human-in-the-loop
• V3 — Proactive cognition loop, pattern detection, trigger system
• V4 — Sessions, temporal awareness, cross-domain pattern mining, entity profiles
• V5 — Multi-agent shared memory, federated learning across users

Worked example: Wirecard (RFC 008 substrate — with honest limits)

For nearly a decade, Wirecard's filings and EY's audit attested to €1.9B in Philippine escrow accounts. In June 2020 both banks and the central bank formally denied the accounts existed.

When the source_lineage fields are hand-populated — EY as [wirecard, ey] to capture audit dependence on Wirecard-provided documents, BSP as [bsp, bpi, bdo] to capture restatement of the commercial banks — RFC 008's ⊕ discounts the dependent claims, and the contest operator's temporal split distinguishes present-tense contradictions from historical state changes. On this hand-populated data, the substrate produces useful annotations.

Honest limits (surfaced by Phase 2 empirical testing, Apr 2026):

• On naturalistic evidence where a real agent populates the fields, the substrate's gates don't reliably fire. Cases B and C of the Phase 2 eval need an extractor/canonicalizer (not yet built) to work; Case A exposed that ⊕ is mathematically incapable of flipping decisions at realistic N, regardless of coefficient tuning.
• Current claim: structured schema for evidence provenance/temporal/conflict annotation, useful for audit and inspection. The dependence-discount operator works on curated inputs but needs replacement before it can drive decisions.
• Not a current claim: "decision-improvement substrate for AGI-capable agents." That framing is withdrawn pending RFC 009.

See docs/showcase/wirecard.md for the full walkthrough including the Phase 2 negative result and the gold-state ablation that partitioned operator failure from extraction failure. Run the hand-populated demonstration directly:

cargo run --example showcase_wirecard

Research & Publications

📄 Skill as Memory, Not Document (May 2026)

Sarkar, P. (2026). Skill as Memory, Not Document: A Database-Native Substrate for Agent Skill Catalogs. Zenodo.

A measurement paper at 5K-skill scale: token cost vs filesystem catalogs (with the honest 1.49× ablation), retrieval latency (87.3 ms p50), and invalid-skill admission (0% YantrikDB vs 97% document-only baseline). Reproducible scripts + raw CSVs at yantrikdb-server/benchmarks/skill_recall/. Companion blog: yantrikdb.com/papers/skill-substrate.

Earlier work

• U.S. Patent Application 19/573,392 (March 2026): "Cognitive Memory Database System with Relevance-Conditioned Scoring and Autonomous Knowledge Management"
• Zenodo (software): YantrikDB: A Cognitive Memory Engine for Persistent AI Systems

Author

Pranab Sarkar — ORCID · LinkedIn · developer@pranab.co.in

License

AGPL-3.0. See LICENSE for the full text.

The MCP server is MIT-licensed — using the engine via the MCP server does not trigger AGPL obligations on your code.