SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '709fb0858e96db0f35d5fbb87756d55efd0a8eab92868f0b843452122e562b12' 
  AND token = 'UOwN4jV20LHywddKJHGIGMSVLmXMeiHHKcgLay/z95E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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