SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8274dd0da4531361cb31bca3d4e54268e4c42ddb638b638bf9bf77b987a6a1f5' 
  AND token = '37UC5XWju/qiRQKLRalj6GrAJBQwVZghEkaZYJQZMn8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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