SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6e737c86cb7709f9e3335efe6ffa302b7545a1852476d6f7b4d516e49867d96' 
  AND token = '/ntqn6+DF8/g8U3AjqyIWVIuWiwRU1KOyBJMfPjD674=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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