SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f0bd8f3a3f345d9ae568168a3a26beb2121f35d43709473865525794a278e3ec' 
  AND token = 'k+uPw2L4zUWbqRXkgPsfX0BMAlj2FkN2EeonkKPpGm8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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