Transactor stops responding with "Too many open files" error

We run Datomic Cloud in production topology that serves accounting documents (ie. invoices) in JSON format through a REST API (Lambda Ion + AWS API Gateway).

There is a customer that queries hundreds of documents in a batch process at a rate of approximately 20/sec.

After some time, the transactor hangs with a “Too many open files” error. Has someone experienced a similar error?

{
    "Msg": ":valcache/get-exception",
    "Ex": {
        "Via": [
            {
                "Type": "java.nio.file.FileSystemException",
                "Message": "/opt/ssd1/datomic/valcache/761/7dc57059-f6db-4398-b4a5-5cedc0704761: Too many open files",
                "At": [
                    "sun.nio.fs.UnixException",
                    "translateToIOException",
                    "UnixException.java",
                    91
                ]
            }
        ],
        "Trace": [
            [
                "sun.nio.fs.UnixException",
                "translateToIOException",
                "UnixException.java",
                91
            ],
            [
                "sun.nio.fs.UnixException",
                "rethrowAsIOException",
                "UnixException.java",
                102
            ],
            [
                "sun.nio.fs.UnixException",
                "rethrowAsIOException",
                "UnixException.java",
                107
            ],
            [
                "sun.nio.fs.UnixFileSystemProvider",
                "newFileChannel",
                "UnixFileSystemProvider.java",
                177
            ],
            [
                "java.nio.channels.FileChannel",
                "open",
                "FileChannel.java",
                287
            ],
            [
                "java.nio.channels.FileChannel",
                "open",
                "FileChannel.java",
                335
            ],
            [
                "datomic.cloud.valcache$direct_get",
                "invokeStatic",
                "valcache.clj",
                435
            ],
            [
                "datomic.cloud.valcache$direct_get",
                "invoke",
                "valcache.clj",
                426
            ],
            [
                "datomic.cloud.mc_cache.McCache$f__21348",
                "invoke",
                "mc_cache.clj",
                163
            ],
            [
                "clojure.lang.AFn",
                "run",
                "AFn.java",
                22
            ],
            [
                "java.util.concurrent.ThreadPoolExecutor",
                "runWorker",
                "ThreadPoolExecutor.java",
                1149
            ],
            [
                "java.util.concurrent.ThreadPoolExecutor$Worker",
                "run",
                "ThreadPoolExecutor.java",
                624
            ],
            [
                "java.lang.Thread",
                "run",
                "Thread.java",
                748
            ]
        ],
        "Cause": "/opt/ssd1/datomic/valcache/761/7dc57059-f6db-4398-b4a5-5cedc0704761: Too many open files"
    },
    "Type": "Event",
    "Tid": 84,
    "Timestamp": 1622445049738
}
{"Msg":":valcache\/get-exception","Ex":{"Via":[{"Type":"java.nio.file.FileSystemException","Message":"\/opt\/ssd1\/datomic\/valcache\/761\/7dc57059-f6db-4398-b4a5-5cedc0704761: Too many open files","At":["sun.nio.fs.UnixException","translateToIOException","UnixException.java",91]}],"Trace":[["sun.nio.fs.UnixException","translateToIOException","UnixException.java",91],["sun.nio.fs.UnixException","rethrowAsIOException","UnixException.java",102],["sun.nio.fs.UnixException","rethrowAsIOException","UnixException.java",107],["sun.nio.fs.UnixFileSystemProvider","newFileChannel","UnixFileSystemProvider.java",177],["java.nio.channels.FileChannel","open","FileChannel.java",287],["java.nio.channels.FileChannel","open","FileChannel.java",335],["datomic.cloud.valcache$direct_get","invokeStatic","valcache.clj",435],["datomic.cloud.valcache$direct_get","invoke","valcache.clj",426],["datomic.cloud.mc_cache.McCache$f__21348","invoke","mc_cache.clj",163],["clojure.lang.AFn","run","AFn.java",22],["java.util.concurrent.ThreadPoolExecutor","runWorker","ThreadPoolExecutor.java",1149],["java.util.concurrent.ThreadPoolExecutor$Worker","run","ThreadPoolExecutor.java",624],["java.lang.Thread","run","Thread.java",748]],"Cause":"\/opt\/ssd1\/datomic\/valcache\/761\/7dc57059-f6db-4398-b4a5-5cedc0704761: Too many open files"},"Type":"Event","Tid":84,"Timestamp":1622445049738}