Fetch on completed requests very slow

Observed on a local production instance:

{
  "#operator": "Sequence",
  "#stats":

{     "#phaseSwitches": 1,     "execTime": "4.754µs"   }

,
  "~children": [
    {
      "#operator": "Authorize",
      "#stats":

{         "#phaseSwitches": 3,         "execTime": "10.483µs",         "servTime": "4.390092ms"       }

,
      "privileges": {
        "List": [
          

{             "Target": "#system:completed_requests",             "Priv": 4           }

        ]
      },
      "~child": {
        "#operator": "Sequence",
        "#stats":

{           "#phaseSwitches": 1,           "execTime": "15.26µs"         }

,
        "~children": [
          {
            "#operator": "IndexScan",
            "#stats":

{               "#phaseSwitches": 1,               "execTime": "85.136µs"             }

,
            "index": "#nodes",
            "index_id": "#nodes",
            "keyspace": "completed_requests",
            "namespace": "#system",
            "spans": [
              {
                "Exact": true,
                "Range":

{                   "High": [                     "\"172.23.120.22:8091\""                   ],                   "Inclusion": 3,                   "Low": [                     "\"172.23.120.22:8091\""                   ]                 }

              }
            ],
            "using": "system",
            "~children": [
              {
                "#operator": "IndexScan",
                "#stats":

{                   "#itemsOut": 1893,                   "#phaseSwitches": 7575,                   "execTime": "9.108016ms",                   "kernTime": "4m0.866502072s",                   "servTime": "250.828472ms"                 }

,
                "index": "#nodes",
                "index_id": "#nodes",
                "keyspace": "completed_requests",
                "namespace": "#system",
                "spans": [
                  {
                    "Exact": true,
                    "Range":

{                       "High": [                         "\"172.23.120.22:8091\""                       ],                       "Inclusion": 3,                       "Low": [                         "\"172.23.120.22:8091\""                       ]                     }

                  }
                ],
                "using": "system"
              }
            ],
            "#time_normal": "00:00.0000",
            "#time_absolute": 0.00008513599999999999
          },
          {
            "#operator": "Fetch",
            "#stats":

{               "#itemsIn": 1893,               "#itemsOut": 1893,               "#phaseSwitches": 7813,               "execTime": "13.273379ms",               "kernTime": "254.960314ms",               "servTime": "5m21.301150645s"             }

,
            "keyspace": "completed_requests",
            "namespace": "#system",
            "#time_normal": "05:21.3144",
            "#time_absolute": 321.314424024
          },
          {
            "#operator": "Sequence",
            "#stats":

{               "#phaseSwitches": 1,               "execTime": "4.268µs"             }

,
            "~children": [
              {
                "#operator": "Filter",
                "#stats":

{                   "#itemsIn": 1893,                   "#itemsOut": 1893,                   "#phaseSwitches": 7575,                   "execTime": "8.272624ms",                   "kernTime": "5m21.561158873s"                 }

,
                "condition": "((`completed_requests`.`node`) = \"172.23.120.22:8091\")",
                "#time_normal": "00:00.0082",
                "#time_absolute": 0.008272624000000001
              },
              {
                "#operator": "InitialProject",
                "#stats":

{                   "#itemsIn": 1893,                   "#itemsOut": 1893,                   "#phaseSwitches": 5684,                   "execTime": "4.060533ms",                   "kernTime": "5m21.461323918s"                 }

,
                "result_terms": [
                  

{                     "expr": "self",                     "star": true                   }

                ],
                "#time_normal": "00:00.0040",
                "#time_absolute": 0.004060533000000001
              },
              {
                "#operator": "FinalProject",
                "#stats":

{                   "#itemsIn": 1893,                   "#itemsOut": 1893,                   "#phaseSwitches": 5680,                   "execTime": "3.115867ms",                   "kernTime": "99.380004ms"                 }

,
                "#time_normal": "00:00.0031",
                "#time_absolute": 0.003115867
              }
            ],
            "#time_normal": "00:00.0000",
            "#time_absolute": 0.000004268
          }
        ],
        "#time_normal": "00:00.0000",
        "#time_absolute": 0.00001526
      },
      "#time_normal": "00:00.0044",
      "#time_absolute": 0.004400575
    },
    {
      "#operator": "Stream",
      "#stats":

{         "#itemsIn": 1893,         "#itemsOut": 1893,         "#phaseSwitches": 7575,         "execTime": "2.531557ms",         "kernTime": "5m21.571872614s"       }

,
      "#time_normal": "00:00.0025",
      "#time_absolute": 0.002531557
    }
  ],
  "~versions": [
    "2.0.0-N1QL",
    "5.5.0-2958-enterprise"
  ],
  "#time_normal": "00:00.0000",
  "#time_absolute": 0.000004754
}