SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4578587905553c3f31325b038d81f56a02d59bf25bfebf4a7762fe69d82c2c8' 
  AND token = 'wMGshK0d1v+Tiw6dKh+OsmJwhaMm/TGGDs/83fjiSJ8=' 
  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"
    }
  }
}