SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1836ac01d0e99a4f57b3f37dd0fda4cf5590a7736e46a201ae5557c393dca339' 
  AND token = 'JIxDgX2b+Qupfzm5hGnP8bjCUc1vLV56d7WBu2zqro0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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