SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'df2d0994bc03a8d011bd94f010e4961597de773ce64ed539c6206ac66dcece83' 
  AND token = 'a+awO7aBYwZt+8b8scTMNRdZYjn/WSV3cqolkQahGSM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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