SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b331987fd42e0433d0129658e6f4b551727a23da5d7700fc5122796c76da47f0' 
  AND token = '5r3gQ1I/EdtPmpCGIlVZ/n/PyzUjHYiBSuZt17v43NI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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