SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6716d595a7e08b484a64454f646675313c353434d9cfc90562dd498e804d380e' 
  AND token = 'voN8rfMXBTEjU13XVPLnIjKUbZH6D7txIWfInYWAFvk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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