SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '621463459a18661694f0a108e5a70aad0724d84fdcbf6b6835a08d2dbbfb1502' 
  AND token = 'q8wBc/s+n/07WNB65EwLNXuSVzVKa3/Fq7bAdTSAfGI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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