SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5173bcb6998281809a20941dba323e1ebb476c189e4058d8d7a436ccb12fa300' 
  AND token = '8fL3B9fwV4WArSqjjiVi77qXmfGlBJh6MJpF0VbmOpM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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