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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '879165c47d6f380072014e9fba50077321680320387284465507b173aeb6ada2' 
  AND token = '+rnoxx4033LQGWmVoaqBjACCo/XNO4a8AqKDSRzJxBg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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