SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6942b447dd02cd0e79ca07dea5934a609e5ae976db51e95ec05271c907c39de6' 
  AND token = '2zxBXIDpL0D4SHvbdRNY+ACGjQpArHlm65jVBqS9wwI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}