SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '256eecf324c1023094922260203c66172a4c597b6071377557303c50b968adfe' 
  AND token = 'YuKGLqkJAWp4GJhsPhBwAREQvpgqisGpPb7e3PNzonI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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