SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '819a0766ffe9522f7851b88ba82603a53c7cfc83e60ed833d8866dbad7f13d40' 
  AND token = 'msTmMxGYjCC902zoM5ikpPhqLH4waK3Y4xxZ15UW8Qg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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