SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6235ffada72548e8a95baade86c681eaae2655bf944902de9f9f474316f04dc' 
  AND token = '6CtveCcdnq4apwZnW5CwmU+ZBFTS2WnlvQJAYmEccsw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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