SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6208e50ea27580dee03e6d6f838adfeeca14a4911e9e4d7a4ba7046f1bb8fd43' 
  AND token = 'Fe3kxwnPQHY0fv9/+dLxnOeMkGuhXqPYlLFf1YiQ77E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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