SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '257e121ba4e239ad8c161db1e3ed1a4b0b8952ef746d306448177760b70d88c8' 
  AND token = 'OZ/7GmMJJJtbHBMGiVy7Lu/emI5UMrriHhXXx1BBDqM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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