SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'bf509312891f063f11456cd154817d010fea50f02c6b944e60dd108546601d09' 
  AND token = 'uB+ohpQPZqbSgp4xXZw4KOOfLXgPBiHR59EBLXXeWUw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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