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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68ac7d8c4d622587d02c0fef4bd7e998d9b6a697f7ec0c7f1e7347cb0898c85e' 
  AND token = '6eFefs3ZMurgw2APKBaYj6HGsDbAAc1qKQkh8/QmDYs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00015

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}