@morpho-org/viem-dlc

A collection of flexible viem extensions with a focus on intelligent caching. Provides composable transport wrappers for optimized eth_getLogs and deployless eth_call handling with caching, rate limiting, automatic request splitting, and oversized-log filtering.

Installation

pnpm add @morpho-org/viem-dlc

Also available on the GitHub Package Registry.

Transports

deployless

Thin transport wrapper for deployless eth_call splitting. It only intercepts calls carrying the policy(...) sentinel in stateOverride, re-packs the marked input array into one or more deployless-factory calls under both a byte budget (batch.batchSize) and a gas budget (batch.gas against the transport's gasLimit), and forwards everything else unchanged.

import { createPublicClient, encodeFunctionData, http, parseAbiItem } from 'viem'
import { call } from 'viem/actions'
import { deployless } from '@morpho-org/viem-dlc/transports'
import { policy } from '@morpho-org/viem-dlc/actions'

const positionsAbi = parseAbiItem(
  'function positions((bytes32 id, address user)[] inputs) view returns ((uint256,uint128,uint128)[])'
)

const client = createPublicClient({
  transport: deployless(http(rpcUrl), { gasLimit: 30_000_000 }),
})

const result = await call(client, {
  factory,
  factoryData,
  to,
  data: encodeFunctionData({ abi: [positionsAbi], functionName: 'positions', args: [inputs] }),
  stateOverride: [
    policy({
      abi: positionsAbi,
      batch: {
        batchSize: 1 << 15,
        gas: { constant: 50_000, linear: 30_000, quadratic: 0 },
      },
    }),
  ],
})

If policy.cache is present, deployless(...) ignores it and still behaves as split-only mode. Use cache(...) when you want the same marked calls to populate and read from a backing store.

cache

All-in-one caching transport for eth_getLogs and eth_call. Internally composes five layers: oversized-log filtering (logsSieve), log enrichment (logsEnricher), rate limiting (rateLimiter), request splitting (logsDivider), and caching. Requires a chain on the client so it can namespace cache keys by chain ID.

import { createPublicClient, http } from 'viem'
import { mainnet } from 'viem/chains'
import { cache, createSimpleInvalidation } from '@morpho-org/viem-dlc/transports/cache'
import { LruStore } from '@morpho-org/viem-dlc/stores'

const transport = cache(http(rpcUrl), [
  {
    binSize: 10_000,
    store: new LruStore(100_000_000),
    invalidationStrategy: createSimpleInvalidation(),
    gasLimit: 30_000_000,
  },
  {
    maxBlockRange: 100_000,
  },
  {
    retryCount: 3,
    retryDelay: 1_000,
    blockTimestamp: false,
  },
  {
    maxBytes: 8_192,
  },
  {
    maxRequestsPerSecond: 10,
    maxBurstRequests: 5,
    maxConcurrentRequests: 5,
  },
])

const client = createPublicClient({ chain: mainnet, transport })

The binSize determines cache entry granularity. Requests are aligned to bin boundaries to maximize cache hits. Smaller bins allow finer-grained invalidation but increase storage overhead. The logsDivider config's alignTo is automatically set to binSize.

Two invalidation strategies are provided:

• createSimpleInvalidation(minAgeMs?, maxAgeDays?, numHotBlocks?, avgInvalidationsPerRequest?) — entries near the chain tip are always refetched; older entries are probabilistically invalidated based on age.
• createExponentialInvalidation(alphaAge?, maxAgeDays?, alphaBlocks?, scaleBlocks?) — exponential model with separate time and block-age factors.

failover

Request-level fallback dispatcher for fronting multiple RPC providers with provider-specific limits. Each branch is a fully-built per-provider stack carrying its own maxBlockRange / gasLimit. Branches are constructed once at composition time, so stateful inner transports (coalescing mutexes, rate-limiter token buckets) persist across requests instead of being rebuilt per call — unlike viem's stock fallback, which rebuilds the active branch on every request and effectively disables those features.

import { createPublicClient, http } from 'viem'
import { mainnet } from 'viem/chains'
import { failover } from '@morpho-org/viem-dlc/transports'
import { cache, createSimpleInvalidation } from '@morpho-org/viem-dlc/transports/cache'
import { LruStore } from '@morpho-org/viem-dlc/stores'

const store = new LruStore(100_000_000)
const sharedConfig = { binSize: 10_000, store, invalidationStrategy: createSimpleInvalidation() }

const transport = failover([
  cache(http(rpcUrlA), [{ ...sharedConfig, gasLimit: 30_000_000 }, { maxBlockRange: 100_000 }]),
  cache(http(rpcUrlB), [{ ...sharedConfig, gasLimit: 50_000_000 }, { maxBlockRange: 10_000 }]),
])

const client = createPublicClient({ chain: mainnet, transport })

Each branch's logsDivider chunks requests at its own maxBlockRange, so neither provider is sized for the lowest common denominator. The shared Store means partial fetches from branch A persist in cache and are visible to branch B on fallover, making recovery cheap.

failover only sees errors that escape per-branch halving (logsDivider range-halving and deployless size-bisection run inside each branch first). By default, contract reverts and user-rejection errors propagate immediately instead of triggering fallover — pass a custom shouldThrow to override:

import { defaultShouldThrow, failover } from '@morpho-org/viem-dlc/transports'

failover([branchA, branchB], {
  shouldThrow: (err) =>
    defaultShouldThrow(err) ||
    [401, 402, 403].includes((err as { status?: number })?.status ?? 0),
})

logsDivider

Splits large eth_getLogs requests into smaller chunks with automatic retry, optional alignment, internal rate/concurrency limiting via rateLimiter, log enrichment via logsEnricher, and oversized-log filtering via logsSieve.

import { createPublicClient, http } from 'viem'
import { logsDivider } from '@morpho-org/viem-dlc/transports'

const transport = logsDivider(http(rpcUrl), [
  {
    maxBlockRange: 100_000,
    alignTo: 10_000,
  },
  {
    retryCount: 3,
    retryDelay: 1_000,
    blockTimestamp: false,
  },
  {
    maxBytes: 8_192,
  },
  {
    maxRequestsPerSecond: 10,
    maxConcurrentRequests: 5,
  },
])

const client = createPublicClient({ transport })

const logs = await client.request({
  method: 'eth_getLogs',
  params: [
    filter,
    undefined,
    {
      onLogsResponse: ({ logs, fromBlock, toBlock }) => {
        /* progressive updates */
      },
    },
  ],
})

logsEnricher

Enriches eth_getLogs responses with data that standard RPCs omit. Currently supports populating blockTimestamp by fetching block headers. Logs whose block was reorged away are silently dropped.

import { createPublicClient, http } from 'viem'
import { logsEnricher } from '@morpho-org/viem-dlc/transports'

const transport = logsEnricher(http(rpcUrl), [{
  retryCount: 3,
  retryDelay: 1_000,
  blockTimestamp: true,
}])

const client = createPublicClient({ transport })

logsSieve

Filters eth_getLogs responses by estimated UTF-8 payload size. Any RpcLog whose serialized size exceeds maxBytes is silently dropped. logsDivider(...) and cache(...) already compose this transport by default; use logsSieve(...) directly when filtering is all you need.

import { createPublicClient, http } from 'viem'
import { logsSieve } from '@morpho-org/viem-dlc/transports'

const transport = logsSieve(http(rpcUrl), [{ maxBytes: 8_192 }])

const client = createPublicClient({ transport })

rateLimiter

Token-bucket rate limiting with concurrency limiting and priority scheduling:

import { createPublicClient, http } from 'viem'
import { rateLimiter } from '@morpho-org/viem-dlc/transports'

const transport = rateLimiter(http(rpcUrl), [
  {
    maxRequestsPerSecond: 10,
    maxBurstRequests: 5,
    maxConcurrentRequests: 3,
  },
])

const client = createPublicClient({ transport })

await client.request({
  method: 'eth_getLogs',
  params: [
    filter,
    {
      __rateLimiter: true,
      priority: 0,
    },
  ],
})

Stores

Key-value stores implementing the Store interface:

interface Store {
  get(key: string): MaybePromise<Buffer[] | null>
  set(key: string, value: Buffer[]): MaybePromise<void>
  delete(key: string): MaybePromise<void>
  flush(): MaybePromise<void>
}

| Store | Import | Description | | --- | --- | --- | | LruStore | @morpho-org/viem-dlc/stores | LRU cache with configurable byte-size limit | | MemoryStore | @morpho-org/viem-dlc/stores | Simple in-memory Map (prefer LruStore) | | HierarchicalStore | @morpho-org/viem-dlc/stores | Layered stores — reads fall through, writes fan out | | DebouncedStore | @morpho-org/viem-dlc/stores | Batches writes with debounce + max staleness timeout | | CompressedStore | @morpho-org/viem-dlc/stores | Transparent zstd compression (Node/Bun only) | | UpstashStore | @morpho-org/viem-dlc/stores/upstash | Upstash Redis with automatic value sharding and atomic writes |

Composing stores

Stores are designed to be layered. For example, createOptimizedUpstashStore (exported from @morpho-org/viem-dlc/stores/upstash) returns a pre-composed stack:

LruStore (fast, in-process)
  └─ DebouncedStore (coalesces writes)
       └─ UpstashStore (durable, remote)

import { createOptimizedUpstashStore } from '@morpho-org/viem-dlc/stores/upstash'

const store = createOptimizedUpstashStore({
  maxRequestBytes: 1_000_000,
  maxWritesPerSecond: 300,
})

Actions

getLogs2

Drop-in replacement for viem's getLogs that adds cache-layer search pre-filtering and streaming reduce. Requires a client whose transport uses the cache() wrapper (i.e. whose rpcSchema is CacheSchema).

search is a regex matched against raw NDJSON before parsing — use hex-encoded values (address fragments, topic prefixes) to skip expensive JSON.parse calls on irrelevant batches. reduce folds over decoded logs in order, keeping memory proportional to the accumulator rather than the full result set.

import { parseAbiItem } from 'viem'
import { getLogs2 } from '@morpho-org/viem-dlc/actions'

const logs = await getLogs2(client, {
  address: '0x...',
  event: parseAbiItem('event Transfer(address indexed, address indexed, uint256)'),
  fromBlock: 18_000_000n,
  toBlock: 19_000_000n,
  search: 'deadbeef',
  reduce: (acc, log) => {
    acc.push(log) // log.args is already decoded
    return acc
  },
})

eth_call policy

Creates a stateOverride entry that tells the deployless or cache transport how to handle a deployless eth_call. Works with viem's call action against a contract exposing a single dynamic-array input and a single dynamic-array output (e.g. balancesOf(address[]) -> uint256[]), invoked via viem's deployless-factory pattern (call({ factory, factoryData, to, data, ... })). The transports decode the outer array structurally; when used with cache, element bytes round-trip through the cache untouched, so tuples, nested arrays, and other complex element types are supported.

policy(opts: {
  abi: AbiFunction
  batch?: {
    batchSize?: number
    exfil?: 'return' | 'revert'
    compress?: boolean
    gas?: { constant: number; linear: number; quadratic: number }
  }
  cache?: {
    blobKey: string
    ttl: number
    delta?: number
  }
})

• opts.abi — the AbiFunction fragment for the callee. Must have exactly one input and one output, both dynamic arrays.
• opts.batch — optional batching config. Omit to send all elements in a single upstream eth_call. When set, chunks honor batchSize and gas together — either budget can be left unset.
• opts.batch.batchSize — maximum bytes of the eth_call data field per chunk. Input elements are greedy-packed under this limit and fetched in parallel. Omit to skip byte-budget enforcement.
• opts.batch.exfil — outer wrapper mode. Defaults to 'return'. Set to 'revert' to exfiltrate via REVERT, lifting the EIP-170 24_576-byte returndata cap at the cost of relying on the RPC preserving revert data.
• opts.batch.compress — FastLZ-compress calldata on the wire. Helps fit more elements per chunk under EIP-3860's 49_152-byte initcode cap, at the cost of extra pre-request encoding time.
• opts.batch.gas — polynomial gas-cost model G(N) = constant + linear·N + quadratic·N² for the lens. Combined with the transport's gasLimit, the chunker picks the largest per-chunk N such that G(N) ≤ gasLimit. No internal safety factor — pad the estimate if you want headroom. linear is typically the dominant term; quadratic captures memory expansion (memWords² / 512); pass 0 for any unused term.
• opts.cache — optional cache config, honored by cache(...) only. If omitted, or when used with deployless(...), batch is still honored without caching.
• opts.cache.blobKey — identifies the backing store blob. Requests with the same blobKey share storage; different blobKeys are isolated into different blobs.
• opts.cache.ttl — maximum age in milliseconds before a cached entry is considered stale.
• Semantic requirement — beyond the ABI shape, the callee must be elementwise: for an input array [x0, ..., xn], it must return [y0, ..., yn] with the same length and order, where each yi depends only on xi plus shared chain state, not on other elements, their multiplicity, or their order.
• opts.cache.delta — XFetch early-refresh scale in milliseconds. On each freshness check the handler samples u ~ Uniform(0, 1] and treats the entry as stale once age - delta * ln(u) >= ttl, so entries may refresh up to several delta before ttl but never later. Desynchronizes refreshes across many keys populated together, avoiding stampedes. Based on Vattani et al., "Optimal Probabilistic Cache Stampede Prevention" (2015), assuming constant recompute cost. Defaults to 0 (disabled).

import { encodeFunctionData, parseAbiItem } from 'viem'
import { call } from 'viem/actions'
import { policy } from '@morpho-org/viem-dlc/actions'

const positionsAbi = parseAbiItem(
  'function positions((bytes32 id, address user)[] inputs) view returns ((uint256,uint128,uint128)[])'
)

const cachePolicy = policy({
  abi: positionsAbi,
  batch: {
    batchSize: 1 << 15,
    gas: { constant: 50_000, linear: 30_000, quadratic: 0 },
  },
  cache: {
    blobKey: 'morpho-positions',
    ttl: 300_000,
  },
})

const result = await call(client, {
  factory,      // deployed factory address
  factoryData,  // calldata that makes `factory` deploy the lens helper
  to,           // deterministic deployment address of the lens
  data: encodeFunctionData({ abi: [positionsAbi], functionName: 'positions', args: [inputs] }),
  stateOverride: [cachePolicy],
})

Cache keys are derived from (targetTo, factory, factoryData, selector, inputElement), so repeat elements collapse into a single blob entry and novel elements are appended to the blob on the next fetch. The handler rejects any tx envelope field besides data (from, gas, value, etc.).

getDeploymentBlockNumber

Finds the block at which a contract was deployed using binary search over getCode.

import { createPublicClient, http } from 'viem'
import { mainnet } from 'viem/chains'
import { getDeploymentBlockNumber } from '@morpho-org/viem-dlc/actions'

const client = createPublicClient({ chain: mainnet, transport: http() })

const block = await getDeploymentBlockNumber(client, {
  address: '0x...',
})

Utilities

Exported from @morpho-org/viem-dlc/utils:

• divideBlockRange / mergeBlockRanges / halveBlockRange — block range manipulation
• resolveBlockNumber / extractRangeFromFilter / isInBlockRange — block number helpers
• isErrorCausedByBlockRange — detect RPC "block range too large" errors
• createCoalescingMutex — per-resource leader/follower batching
• createTokenBucket / createRateLimit — rate limiting primitives
• cyrb64Hash — fast string hashing
• stringify / parse / estimateUtf8Bytes — JSON serialization with bigint support
• pick / omit — object helpers
• measureUtf8Bytes / shardString — string utilities