SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2d8755bd48bd937cb01eefa395ee931cf552facc1bb0fa63fa2c74dca40ee56c' 
  AND token = '9HeoQNXRahLwtjDe/OvB0gwaVEzsL89AqrLXTy/wEig=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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