SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = 'b3e7cc9e8afd923972b5bb58012f3f0e6b3336ca935ac44edb060d4c7a4da1a4' 
  AND token = 'VYhR0U4QubDXLCvkWDd4zbi57lxJJM9rQ/Kflh4UOEs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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