SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '513281d35901d2403518a477de094529718cced8f3ced9926f8a4ca0526be45b' 
  AND token = 'jTLNA9x+IaJS+36u+mYQL+MGhBH0vxX+/rPtJgrxZ/I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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