SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8e5b99444277da6de1ee60f612c3b98afee4e15f68602ab2f73a05b9fba88f5' 
  AND token = 'jn+RjUMi2GuPQ60PvJAs2OBBGLdKdCzkmXq0xB/S4mU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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