SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6b0927438cbb55579cbd0d5bcffd010fd90138df0cb6d2e454aedc05b80baca' 
  AND token = 'qEtyE3rFgXDaiRC+V5NKID2jPlFmbuKTXqHLipdmVn0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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