SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '640e1cf1466c688659bcf93aeefde39563e939969ea0ee521ab8fe27cb22f976' 
  AND token = '6XAJF4EPnaL9QFpEqLsAxYLxaWDh/kfKJSLDMWGa8Lk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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