SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '02c5214b43bf4dbf937a06c3066213b62f3f18b21835a9bd96e9451be8c30956' 
  AND token = 'UJb9KkPylWECY4p3AyZBauMiYmeB+eq8B0hF/DkCV4E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00015

JSON explain

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