SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6f5f2f92486baf8335d63b7d616d5659435cf999789d4650da2d2b1226c41a3f' 
  AND token = '8FwR+QGh+66vZCGe51Xy0HPlvQpc3mdzIqZTNqdfoEs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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