SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'bce81f597e7401d1476fa260c16984fbd0bd125fd794802ee392a6a92c50eef2' 
  AND token = 'hbBprp/CFP9L/R5ElApzjjwhH5Ogy+IWSOqjCtNWQEI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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