SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4ee3dfe0f9dc4b6be1d98f65e04264e49bef31bbec6837f047632e14b2839853' 
  AND token = 'RKHGHkw2PwZ5Aiix/gZBsYj7Nhiiv7nV2ItyWaewRtA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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