SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9357c8991964bbe498bc530849753a1386cd3bd37addab83f86d0ac08667c838' 
  AND token = '6vEkwR2BVvK6MgqftiKul4sKbMWathTvBa3iM7R0rsE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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