SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51355434c868890e26ff0cccb3c76aa517aebd538b3b041c17e780d5beca7d32' 
  AND token = 'wGIyk1y8g5BhHegmW3UNATKsUhYgcxhRVTqw+4w/mbU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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