SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f3b5458fec9797365011afcb110e1f34c6d90161066eba987f9272ebe400a48f' 
  AND token = 'MMLvrJIpe+WLcpKpE5I5oUgvEJeiduz5JKOC4/TS4w0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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