SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6304b3dfe030bbde825001ce842b6c2d85c2369b878a9465cf20359f47133d87' 
  AND token = 'p8omy1TH7+TsKj4AFaFdrICq58AgtAeEmB4utEBlVZU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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