SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '91ec21c01fbabd319a54ddaefc5f7b9297d5a89f1fe4b183d123e2435c4b4802' 
  AND token = 'evLkK+ScFzBj0VIWuO8XU82bUCJqV8wO7HH3YUmGO/E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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