SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81f3a44b3a0f49cd971223b91a9b1f94102577ae4e2812a9bb20b69938641eb1' 
  AND token = 'XHKDmoF9ty/AKGGI8yNMUHzrCFkY3EyIPSzt+tkvEwg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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