SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a1b75e04be1f44e5f78e711ac9f7397ffbf8db68d550f0202d23ec9321ba65e3' 
  AND token = 'B6tgXJaOBJIFPEbYJwmMVRElHw6CtuQyE6Pf+MXuXqU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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