SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8a61a9780beda4c64b6c036c33bfab33331684c8e3f32a7565b92f5ffbda09f' 
  AND token = 'uE21nPLfwBzKPmViuZUnwOU4bmw8IN5wz3lDuVbRLWU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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