SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3500fba7c39f58ed72690b49ed8399f1c6120d834dc9549df284c0057969a416' 
  AND token = 'Xtl0tXQ6vgGGqd6libGiNxng4wYmMDoAFdtkhnhlsNE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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