SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b5984a9cad61cc02472fdeab8b6808ff5e5d29901daab5757ea4b8449b5ca303' 
  AND token = 'AO3AWZv+YqgI1tOD4NvIuqIGSfG9FvJHne7BbGzOspU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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