SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '926732a553f71e031367861373373bdcdf6c775b8a7838d0a85e6720a1f9d615' 
  AND token = 'WaSwWytwnteBzMESLo1jDUVCI09yHNHLuzIrzbH1P2o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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